21645775800 has 240 divisors, whose sum is σ = 82014114600. Its totient is φ = 5247417600.

The previous prime is 21645775703. The next prime is 21645775813. The reversal of 21645775800 is 857754612.

21645775800 is a `hidden beast` number, since 2 + 1 + 64 + 5 + 7 + 7 + 580 + 0 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 117466 + ... + 238934.

Almost surely, 2^21645775800 is an apocalyptic number.

21645775800 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 21645775800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41007057300).

21645775800 is an abundant number, since it is smaller than the sum of its proper divisors (60368338800).

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

21645775800 is a wasteful number, since it uses less digits than its factorization.

21645775800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121508 (or 121490 counting only the distinct ones).

The product of its (nonzero) digits is 470400, while the sum is 45.

The spelling of 21645775800 in words is "twenty-one billion, six hundred forty-five million, seven hundred seventy-five thousand, eight hundred".