21405872564 has 12 divisors (see below), whose sum is σ = 38167075044. Its totient is φ = 10500993984.

The previous prime is 21405872561. The next prime is 21405872629. The reversal of 21405872564 is 46527850412.

It can be written as a sum of positive squares in 2 ways, for example, as 17717739664 + 3688132900 = 133108^2 + 60730^2 .

It is a super-2 number, since 2×21405872564² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (44) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405872561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50485337 + ... + 50485760.

It is an arithmetic number, because the mean of its divisors is an integer number (3180589587).

Almost surely, 2^21405872564 is an apocalyptic number.

It is an amenable number.

21405872564 is a deficient number, since it is larger than the sum of its proper divisors (16761202480).

21405872564 is a wasteful number, since it uses less digits than its factorization.

21405872564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100971154 (or 100971152 counting only the distinct ones).

The product of its (nonzero) digits is 537600, while the sum is 44.

The spelling of 21405872564 in words is "twenty-one billion, four hundred five million, eight hundred seventy-two thousand, five hundred sixty-four".