21259972864 has 81 divisors (see below), whose sum is σ = 46018027839. Its totient is φ = 9798297600.

The previous prime is 21259972861. The next prime is 21259972871. The reversal of 21259972864 is 46827995212.

It is a happy number.

The square root of 21259972864 is 145808.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 4665600 + 21255307264 = 2160^2 + 145792^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21259972861) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 30327714 + ... + 30328414.

Almost surely, 2^21259972864 is an apocalyptic number.

21259972864 is the 145808-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21259972864

21259972864 is an abundant number, since it is smaller than the sum of its proper divisors (24758054975).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21259972864 is an frugal number, since it uses more digits than its factorization.

21259972864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1444 (or 716 counting only the distinct ones).

The product of its digits is 4354560, while the sum is 55.

The spelling of 21259972864 in words is "twenty-one billion, two hundred fifty-nine million, nine hundred seventy-two thousand, eight hundred sixty-four".