21644704531 has 2 divisors, whose sum is σ = 21644704532. Its totient is φ = 21644704530.

The previous prime is 21644704519. The next prime is 21644704579. The reversal of 21644704531 is 13540744612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21644704531 - 2²⁹ = 21107833619 is a prime.

It is a super-2 number, since 2×21644704531² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21644704511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10822352265 + 10822352266.

It is an arithmetic number, because the mean of its divisors is an integer number (10822352266).

Almost surely, 2^21644704531 is an apocalyptic number.

21644704531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21644704531 is an equidigital number, since it uses as much as digits as its factorization.

21644704531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 80640, while the sum is 37.

The spelling of 21644704531 in words is "twenty-one billion, six hundred forty-four million, seven hundred four thousand, five hundred thirty-one".