21405524664 has 64 divisors (see below), whose sum is σ = 54163549440. Its totient is φ = 7048811520.

The previous prime is 21405524633. The next prime is 21405524669. The reversal of 21405524664 is 46642550412.

It is a super-2 number, since 2×21405524664² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21405524669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1321237 + ... + 1337339.

It is an arithmetic number, because the mean of its divisors is an integer number (846305460).

Almost surely, 2^21405524664 is an apocalyptic number.

21405524664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21405524664 is an abundant number, since it is smaller than the sum of its proper divisors (32758024776).

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

21405524664 is a wasteful number, since it uses less digits than its factorization.

21405524664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16780 (or 16776 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 39.

The spelling of 21405524664 in words is "twenty-one billion, four hundred five million, five hundred twenty-four thousand, six hundred sixty-four".