21927431 has 2 divisors, whose sum is σ = 21927432. Its totient is φ = 21927430.

The previous prime is 21927413. The next prime is 21927443. The reversal of 21927431 is 13472912.

Together with previous prime (21927413) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21927431 is a prime.

It is a super-2 number, since 2×21927431² = 961624460519522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21927394 and 21927403.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21927461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10963715 + 10963716.

It is an arithmetic number, because the mean of its divisors is an integer number (10963716).

Almost surely, 2^21927431 is an apocalyptic number.

21927431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21927431 is an equidigital number, since it uses as much as digits as its factorization.

21927431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 29.

The square root of 21927431 is about 4682.6734885106. The cubic root of 21927431 is about 279.8955009707.

The spelling of 21927431 in words is "twenty-one million, nine hundred twenty-seven thousand, four hundred thirty-one".