21645973440 has 2016 divisors, whose sum is σ = 106243038720. Its totient is φ = 4138573824.

The previous prime is 21645973439. The next prime is 21645973451. The reversal of 21645973440 is 4437954612.

21645973440 is a `hidden beast` number, since 2 + 16 + 4 + 597 + 3 + 4 + 40 = 666.

It is a tau number, because it is divible by the number of its divisors (2016).

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 287 ways as a sum of consecutive naturals, for example, 941129269 + ... + 941129291.

It is an arithmetic number, because the mean of its divisors is an integer number (52699920).

Almost surely, 2^21645973440 is an apocalyptic number.

21645973440 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 21645973440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (53121519360).

21645973440 is an abundant number, since it is smaller than the sum of its proper divisors (84597065280).

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

21645973440 is a wasteful number, since it uses less digits than its factorization.

21645973440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101 (or 72 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 45.

The spelling of 21645973440 in words is "twenty-one billion, six hundred forty-five million, nine hundred seventy-three thousand, four hundred forty".