21612431 has 2 divisors, whose sum is σ = 21612432. Its totient is φ = 21612430.

The previous prime is 21612413. The next prime is 21612497. The reversal of 21612431 is 13421612.

Together with previous prime (21612413) 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 a de Polignac number, because none of the positive numbers 2^k-21612431 is a prime.

It is a super-2 number, since 2×21612431² = 934194347459522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21612131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806215 + 10806216.

It is an arithmetic number, because the mean of its divisors is an integer number (10806216).

Almost surely, 2^21612431 is an apocalyptic number.

21612431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612431 is an equidigital number, since it uses as much as digits as its factorization.

21612431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 288, while the sum is 20.

The square root of 21612431 is about 4648.9171857541. The cubic root of 21612431 is about 278.5487453181.

The spelling of 21612431 in words is "twenty-one million, six hundred twelve thousand, four hundred thirty-one".