21640534560 has 384 divisors, whose sum is σ = 78598840320. Its totient is φ = 5555174400.

The previous prime is 21640534537. The next prime is 21640534613. The reversal of 21640534560 is 6543504612.

21640534560 is a `hidden beast` number, since 2 + 1 + 6 + 40 + 53 + 4 + 560 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 37899075 + ... + 37899645.

It is an arithmetic number, because the mean of its divisors is an integer number (204684480).

Almost surely, 2^21640534560 is an apocalyptic number.

21640534560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21640534560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39299420160).

21640534560 is an abundant number, since it is smaller than the sum of its proper divisors (56958305760).

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

21640534560 is a wasteful number, since it uses less digits than its factorization.

21640534560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 909 (or 895 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 36.

The spelling of 21640534560 in words is "twenty-one billion, six hundred forty million, five hundred thirty-four thousand, five hundred sixty".