21807431 has 2 divisors, whose sum is σ = 21807432. Its totient is φ = 21807430.

The previous prime is 21807419. The next prime is 21807463. The reversal of 21807431 is 13470812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21807431 is a prime.

It is a super-2 number, since 2×21807431² = 951128093639522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21807431.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21807931) 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, 10903715 + 10903716.

It is an arithmetic number, because the mean of its divisors is an integer number (10903716).

Almost surely, 2^21807431 is an apocalyptic number.

21807431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21807431 is an equidigital number, since it uses as much as digits as its factorization.

21807431 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21807431 is about 4669.8427168375. The cubic root of 21807431 is about 279.3839815973.

The spelling of 21807431 in words is "twenty-one million, eight hundred seven thousand, four hundred thirty-one".