21539644560 has 120 divisors (see below), whose sum is σ = 82671226560. Its totient is φ = 4923346176.

The previous prime is 21539644559. The next prime is 21539644573. The reversal of 21539644560 is 6544693512.

21539644560 is a `hidden beast` number, since 2 + 1 + 539 + 64 + 4 + 56 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a super-2 number, since 2×21539644560² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2131830 + ... + 2141909.

It is an arithmetic number, because the mean of its divisors is an integer number (688926888).

Almost surely, 2^21539644560 is an apocalyptic number.

21539644560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21539644560 is an abundant number, since it is smaller than the sum of its proper divisors (61131582000).

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

21539644560 is a wasteful number, since it uses less digits than its factorization.

21539644560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4273765 (or 4273756 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 45.

The spelling of 21539644560 in words is "twenty-one billion, five hundred thirty-nine million, six hundred forty-four thousand, five hundred sixty".