21557536560 has 320 divisors, whose sum is σ = 86028303360. Its totient is φ = 4859688960.

The previous prime is 21557536547. The next prime is 21557536571. The reversal of 21557536560 is 6563575512.

21557536560 is a `hidden beast` number, since 2 + 1 + 5 + 57 + 5 + 36 + 560 = 666.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1093995 + ... + 1113525.

It is an arithmetic number, because the mean of its divisors is an integer number (268838448).

Almost surely, 2^21557536560 is an apocalyptic number.

21557536560 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 21557536560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43014151680).

21557536560 is an abundant number, since it is smaller than the sum of its proper divisors (64470766800).

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

21557536560 is a wasteful number, since it uses less digits than its factorization.

21557536560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19633 (or 19621 counting only the distinct ones).

The product of its (nonzero) digits is 945000, while the sum is 45.

The spelling of 21557536560 in words is "twenty-one billion, five hundred fifty-seven million, five hundred thirty-six thousand, five hundred sixty".