21645692640 has 768 divisors, whose sum is σ = 91506723840. Its totient is φ = 4707901440.

The previous prime is 21645692623. The next prime is 21645692641. The reversal of 21645692640 is 4629654612.

21645692640 is a `hidden beast` number, since 2 + 1 + 64 + 569 + 26 + 4 + 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 not an unprimeable number, because it can be changed into a prime (21645692641) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 22856647 + ... + 22857593.

It is an arithmetic number, because the mean of its divisors is an integer number (119149380).

Almost surely, 2^21645692640 is an apocalyptic number.

21645692640 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 21645692640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45753361920).

21645692640 is an abundant number, since it is smaller than the sum of its proper divisors (69861031200).

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

21645692640 is a wasteful number, since it uses less digits than its factorization.

21645692640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1032 (or 1018 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 45.

The spelling of 21645692640 in words is "twenty-one billion, six hundred forty-five million, six hundred ninety-two thousand, six hundred forty".