21403931 has 2 divisors, whose sum is σ = 21403932. Its totient is φ = 21403930.

The previous prime is 21403913. The next prime is 21403973. The reversal of 21403931 is 13930412.

Together with previous prime (21403913) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21403931 - 2¹⁸ = 21141787 is a prime.

It is a super-2 number, since 2×21403931² = 916256524505522, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21403897 and 21403906.

It is not a weakly prime, because it can be changed into another prime (21403831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701965 + 10701966.

It is an arithmetic number, because the mean of its divisors is an integer number (10701966).

Almost surely, 2^21403931 is an apocalyptic number.

21403931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21403931 is an equidigital number, since it uses as much as digits as its factorization.

21403931 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 23.

The square root of 21403931 is about 4626.4382628541. The cubic root of 21403931 is about 277.6501084361.

The spelling of 21403931 in words is "twenty-one million, four hundred three thousand, nine hundred thirty-one".