21645311656400 has 240 divisors, whose sum is σ = 55040968402560. Its totient is φ = 8163800832000.

The previous prime is 21645311656391. The next prime is 21645311656403. The reversal of 21645311656400 is 465611354612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645311656403) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 212735939 + ... + 212837661.

It is an arithmetic number, because the mean of its divisors is an integer number (229337368344).

Almost surely, 2^{21645311656400} is an apocalyptic number.

21645311656400 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 21645311656400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27520484201280).

21645311656400 is an abundant number, since it is smaller than the sum of its proper divisors (33395656746160).

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

21645311656400 is a wasteful number, since it uses less digits than its factorization.

21645311656400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102094 (or 102083 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 44.

The spelling of 21645311656400 in words is "twenty-one trillion, six hundred forty-five billion, three hundred eleven million, six hundred fifty-six thousand, four hundred".