21397616640 has 384 divisors, whose sum is σ = 76646606400. Its totient is φ = 5662310400.

The previous prime is 21397616623. The next prime is 21397616687. The reversal of 21397616640 is 4661679312.

21397616640 is a `hidden beast` number, since 21 + 3 + 9 + 7 + 616 + 6 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

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 31 ways as a sum of consecutive naturals, for example, 53360440 + ... + 53360840.

Almost surely, 2^21397616640 is an apocalyptic number.

21397616640 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 21397616640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38323303200).

21397616640 is an abundant number, since it is smaller than the sum of its proper divisors (55248989760).

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

21397616640 is a wasteful number, since it uses less digits than its factorization.

21397616640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 630 (or 604 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The spelling of 21397616640 in words is "twenty-one billion, three hundred ninety-seven million, six hundred sixteen thousand, six hundred forty".