21079931 has 2 divisors, whose sum is σ = 21079932. Its totient is φ = 21079930.

The previous prime is 21079889. The next prime is 21079979. The reversal of 21079931 is 13997012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21079931 - 2⁶ = 21079867 is a prime.

It is a super-2 number, since 2×21079931² = 888726981929522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21079631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10539965 + 10539966.

It is an arithmetic number, because the mean of its divisors is an integer number (10539966).

Almost surely, 2^21079931 is an apocalyptic number.

21079931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21079931 is an equidigital number, since it uses as much as digits as its factorization.

21079931 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21079931 is about 4591.2885990754. The cubic root of 21079931 is about 276.2420118763.

The spelling of 21079931 in words is "twenty-one million, seventy-nine thousand, nine hundred thirty-one".