Number theoretic functions

ContinuedFraction — get continued fraction expansion
DivisorSigma — compute divisor function
DivisorSum — compute divisor sum
Divisors — get integer divisors
EulerPhi — get Euler totient function
FactorInteger — list prime factors and exponents of a number
FractionalPart — get fractional part of a number
FromContinuedFraction — reconstruct a number from its continued fraction representation
IntegerPart — get integer part of a number
IntegerPartitions — list integer partitions
JacobiSymbol — get Jacobi symbol
KroneckerSymbol — get Kronecker symbol
MantissaExponent — decompose numbers as mantissa and exponent
MersennePrimeExponent — get Mersenne prime exponent
MoebiusMu — get Mobius function
NextPrime — get prime number "near" another number
PartitionsP — number of unrestricted partitions
PowersRepresentations — represent a number as a sum of powers
Prime — get nth prime number
PrimePi — count the number of primes less than or equal to a number
PrimePowerQ — test if a number is a power of a prime number
RandomPrime — pick a random prime in an interval
SquaresR — compute the sum of squares