21656599380 has 432 divisors, whose sum is σ = 77165996544. Its totient is φ = 4881461760.

The previous prime is 21656599343. The next prime is 21656599423. The reversal of 21656599380 is 8399565612.

It is a happy number.

21656599380 is a `hidden beast` number, since 2 + 16 + 5 + 6 + 599 + 38 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 26186527 + ... + 26187353.

It is an arithmetic number, because the mean of its divisors is an integer number (178624992).

Almost surely, 2^21656599380 is an apocalyptic number.

21656599380 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 21656599380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38582998272).

21656599380 is an abundant number, since it is smaller than the sum of its proper divisors (55509397164).

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

21656599380 is a wasteful number, since it uses less digits than its factorization.

21656599380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 924 (or 900 counting only the distinct ones).

The product of its (nonzero) digits is 3499200, while the sum is 54.

The spelling of 21656599380 in words is "twenty-one billion, six hundred fifty-six million, five hundred ninety-nine thousand, three hundred eighty".