Developer Utilities
Small developer utilities that save a trip to a random website. Encode and decode Base64, explain a regex, build UTM links, generate QR codes and vCards, and more — the everyday helpers. Free in your browser, and available by API when you need them in a script.
Developer Utilities
Fermat number generator
compute the n-th Fermat number 2^(2^n)+1
POST /numth/fermat-number$0.002Developer Utilities
Repunit checker
is n all ones in decimal?
POST /numth/repunit-check$0.002Developer Utilities
Vampire Number Checker
Find the Fangs of a Number
POST /numth/vampire-number$0.002Developer Utilities
Additive prime checker
prime with prime digit sum, free
POST /numth/additive-prime$0.002Developer Utilities
Balanced prime checker
test a prime using its neighbors
POST /numth/balanced-prime$0.002Developer Utilities
Permutable Prime Checker
Test Every Digit Permutation
POST /numth/permutable-prime$0.002Developer Utilities
Safe prime checker
test p and (p − 1) / 2
POST /numth/safe-prime$0.002Developer Utilities
Wieferich prime checker
test 2^{p−1} ≡ 1 (mod p²)
POST /numth/wieferich-prime$0.002Developer Utilities
Dudeney number checker
test cube roots and digit sums
POST /numth/dudeney-number$0.002Developer Utilities
Evil number checker
even number of ones in binary
POST /numth/evil-number$0.002Developer Utilities
Home Prime Calculator
Iterate Prime-Factor Concatenation
POST /numth/home-prime$0.002Developer Utilities
Lucas prime checker
is the n-th Lucas number prime?
POST /numth/lucas-prime$0.002Developer Utilities
Mersenne prime checker using the Lucas-Lehmer test
POST /numth/mersenne-prime-check$0.002Developer Utilities
Prime triplet finder
list (p,p+2,p+6) and (p,p+4,p+6) up to n
POST /numth/prime-triplet$0.002Developer Utilities
Alternating digit sum calculator
divisibility by 11
POST /numth/alternating-digit-sum$0.002Developer Utilities
Balanced ternary converter
convert integers using -1, 0 and 1
POST /numth/balanced-ternary$0.002Developer Utilities
Digital root in base
repeated base-b digit sum to a single digit
POST /numth/digital-root-base$0.002Developer Utilities
Equidigital Number Checker
Compare Factorization Digits
POST /numth/equidigital-number$0.002Developer Utilities
Multiplicative persistence calculator
digit product steps to one digit
POST /numth/multiplicative-persistence$0.002Developer Utilities
Depressed cubic solver
Cardano roots of t³ + pt + q = 0
POST /algebra/depressed-cubic$0.002Developer Utilities
Inverse variation calculator
find k and predict y
POST /algebra/inverse-variation$0.002Developer Utilities
Linear equation from slope and point
point-slope and y=mx+b, free
POST /algebra/linear-equation-from-slope-point$0.002Developer Utilities
Literal equation solver
rearrange formulas for any variable
POST /algebra/literal-equation$0.002Developer Utilities
Solve quadratic by factoring
binomials and roots, free calculator
POST /algebra/quadratic-by-factoring$0.002Developer Utilities
Quadratic with complex roots calculator
exact conjugate pair
POST /algebra/quadratic-complex-roots$0.002Developer Utilities
Vertex form to standard form calculator
find a, b, and c
POST /algebra/quadratic-from-vertex-form$0.002Developer Utilities
Quadratic in form solver
substitution and real solutions
POST /algebra/quadratic-in-form$0.002Developer Utilities
Parabola x-intercepts from vertex form
find roots of a(x−h)²+k
POST /algebra/quadratic-vertex-to-intercepts$0.002Developer Utilities
Cube equation solver
solve x³ = k for all three cube roots
POST /algebra/solve-cube-equation$0.002Developer Utilities
Sum and product of roots calculator
Vieta for ax²+bx+c, free
POST /algebra/sum-product-of-roots$0.002Developer Utilities
Two-step linear equation solver
exact answers with steps
POST /algebra/two-step-linear-equation$0.002Developer Utilities
Y-intercept of a line calculator
set x=0 in ax+by+c=0
POST /algebra/y-intercept-of-line$0.002Developer Utilities
Casting out nines check
verify a sum or product with mod 9
POST /numth/casting-out-nines$0.002Developer Utilities
Imaginary quadratic class number calculator
count reduced forms
POST /numth/class-number-imaginary$0.002Developer Utilities
Fibonacci coding converter
positive integer to binary code ending in 11
POST /numth/fibonacci-coding$0.002Developer Utilities
Hofstadter Q sequence
n-th term of Q(n) recurrence, free
POST /numth/hofstadter-q$0.002Developer Utilities
Narayana's cows sequence calculator
find the n-th term
POST /numth/narayana-cows$0.002Developer Utilities
p-adic valuation calculator
exponent of prime p dividing n
POST /numth/p-adic-valuation$0.002Developer Utilities
Perrin sequence term
calculate the n-th Perrin number
POST /numth/perrin-sequence$0.002Developer Utilities
Thue-Morse sequence bit
parity of ones in binary of n
POST /numth/thue-morse$0.002Developer Utilities
Lower Wythoff sequence calculator
find the n-th term
POST /numth/wythoff-lower$0.002Developer Utilities
Absolute value inequality solver
|ax+b| ⊙ c in interval notation
POST /algebra/absolute-value-inequality$0.002Developer Utilities
Cubic inequality solver
roots, sign chart, and interval notation
POST /algebra/cubic-inequality$0.002Developer Utilities
2x2 system elimination method calculator
exact solution
POST /algebra/system-2x2-elimination$0.002Developer Utilities
Line and parabola intersection
0, 1 or 2 points by substitution
POST /algebra/system-nonlinear-line-parabola$0.002Developer Utilities
Two-variable linear inequality calculator
boundary, style, half-plane
POST /algebra/two-variable-inequality$0.002Developer Utilities
Factor difference of cubes calculator
exact binomial and trinomial
POST /algebra/factor-difference-of-cubes$0.002Developer Utilities
Homogeneous linear system 2x2 calculator
parametric solution
POST /algebra/homogeneous-system-2x2$0.002Developer Utilities
Polynomial composition calculator
f(g(x)) expanded, free
POST /algebra/polynomial-composition$0.002Developer Utilities
Polynomial from roots calculator
expand factors to coefficients
POST /algebra/polynomial-from-roots$0.002Developer Utilities
Polynomial subtraction calculator
combine like terms
POST /algebra/polynomial-subtract$0.002Developer Utilities
FOIL method calculator
multiply two binomials step by step
POST /algebra/foil-method$0.002Developer Utilities
Inverse function calculator
swap variables and solve
POST /algebra/function-inverse$0.002Developer Utilities
Polynomial coefficients extractor
parse expression to coefficient list
POST /algebra/polynomial-coefficients$0.002Developer Utilities
Polynomial degree calculator
highest power of a polynomial, free
POST /algebra/polynomial-degree$0.002Developer Utilities
Polynomial standard form calculator
combine and order terms
POST /algebra/polynomial-standard-form$0.002Developer Utilities
Difference quotient calculator
simplify [f(x+h)−f(x)]/h, free
POST /algebra/difference-quotient$0.002Developer Utilities
Function evaluation calculator
f(x) at a point, domain-aware
POST /algebra/function-evaluate$0.002Developer Utilities
Even or Odd Function Checker
Test Polynomial Symmetry
POST /algebra/function-even-odd$0.002Developer Utilities
Function reflection calculator
reflect across the x-axis or y-axis
POST /algebra/function-reflection$0.002