21904081920 has 792 divisors, whose sum is σ = 90099523800. Its totient is φ = 4904976384.

The previous prime is 21904081877. The next prime is 21904081921. The reversal of 21904081920 is 2918040912.

21904081920 is a `hidden beast` number, since 219 + 0 + 408 + 19 + 20 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1416167424 + 20487914496 = 37632^2 + 143136^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21904081921) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 200954826 + ... + 200954934.

It is an arithmetic number, because the mean of its divisors is an integer number (113762025).

Almost surely, 2^21904081920 is an apocalyptic number.

21904081920 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 21904081920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45049761900).

21904081920 is an abundant number, since it is smaller than the sum of its proper divisors (68195441880).

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

21904081920 is a wasteful number, since it uses less digits than its factorization.

21904081920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243 (or 215 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The spelling of 21904081920 in words is "twenty-one billion, nine hundred four million, eighty-one thousand, nine hundred twenty".