21612931 has 2 divisors, whose sum is σ = 21612932. Its totient is φ = 21612930.

The previous prime is 21612919. The next prime is 21612947. The reversal of 21612931 is 13921612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21612931 is a prime.

It is a super-2 number, since 2×21612931² = 934237572821522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21612896 and 21612905.

It is not a weakly prime, because it can be changed into another prime (21612911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806465 + 10806466.

It is an arithmetic number, because the mean of its divisors is an integer number (10806466).

Almost surely, 2^21612931 is an apocalyptic number.

21612931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612931 is an equidigital number, since it uses as much as digits as its factorization.

21612931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 25.

The square root of 21612931 is about 4648.9709614064. The cubic root of 21612931 is about 278.5508933612.

The spelling of 21612931 in words is "twenty-one million, six hundred twelve thousand, nine hundred thirty-one".