pmya.ru
Base converter
Base conversion
Primality test
Miller–Rabin, deterministic ≤ 2⁶⁴, probabilistic otherwise
Factorization
Trial division + Pollard-Rho, good enough for middle-sized numbers
TeX formulas
KaTeX web-renderer
Calculator
Floating/integer calculator with variables
JavaScript runner (dev)
Run simple JavaScript code with console output
Limits (dev)
Check if a number fits in a certain numerical limits in different programming languages