21904888009 has 15 divisors (see below), whose sum is σ = 22720112877. Its totient is φ = 21118844076.

The previous prime is 21904887947. The next prime is 21904888039. The reversal of 21904888009 is 90088840912.

The square root of 21904888009 is 148003.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 21904888009 - 2²⁵ = 21871333577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21904888039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 326938594 + ... + 326938660.

Almost surely, 2^21904888009 is an apocalyptic number.

21904888009 is the 148003-rd square number.

21904888009 is the 74002-nd centered octagonal number.

It is an amenable number.

21904888009 is a deficient number, since it is larger than the sum of its proper divisors (815224868).

21904888009 is an frugal number, since it uses more digits than its factorization.

21904888009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322 (or 114 counting only the distinct ones).

The product of its (nonzero) digits is 331776, while the sum is 49.

Multiplying 21904888009 by its sum of digits (49), we get a square (1073339512441 = 1036021²).

The spelling of 21904888009 in words is "twenty-one billion, nine hundred four million, eight hundred eighty-eight thousand, nine".