21801553920 has 416 divisors, whose sum is σ = 78554966400. Its totient is φ = 5735448576.

The previous prime is 21801553877. The next prime is 21801553981. The reversal of 21801553920 is 2935510812.

21801553920 is a `hidden beast` number, since 2 + 1 + 80 + 1 + 553 + 9 + 20 = 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 31 ways as a sum of consecutive naturals, for example, 49213219 + ... + 49213661.

Almost surely, 2^21801553920 is an apocalyptic number.

21801553920 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 21801553920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39277483200).

21801553920 is an abundant number, since it is smaller than the sum of its proper divisors (56753412480).

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

21801553920 is an equidigital number, since it uses as much as digits as its factorization.

21801553920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 570 (or 542 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The spelling of 21801553920 in words is "twenty-one billion, eight hundred one million, five hundred fifty-three thousand, nine hundred twenty".