21663313920 has 364 divisors, whose sum is σ = 77996471256. Its totient is φ = 5772902400.

The previous prime is 21663313913. The next prime is 21663313939. The reversal of 21663313920 is 2931336612.

It is a happy number.

21663313920 is a `hidden beast` number, since 2 + 1 + 6 + 633 + 13 + 9 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 14929195 + ... + 14930645.

Almost surely, 2^21663313920 is an apocalyptic number.

21663313920 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 21663313920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38998235628).

21663313920 is an abundant number, since it is smaller than the sum of its proper divisors (56333157336).

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

21663313920 is an frugal number, since it uses more digits than its factorization.

21663313920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1498 (or 1461 counting only the distinct ones).

The product of its (nonzero) digits is 34992, while the sum is 36.

The spelling of 21663313920 in words is "twenty-one billion, six hundred sixty-three million, three hundred thirteen thousand, nine hundred twenty".