21808955 has 24 divisors (see below), whose sum is σ = 30712032. Its totient is φ = 14563584.

The previous prime is 21808939. The next prime is 21808967. The reversal of 21808955 is 55980812.

It is not a de Polignac number, because 21808955 - 2⁴ = 21808939 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 64547 + ... + 64883.

It is an arithmetic number, because the mean of its divisors is an integer number (1279668).

Almost surely, 2^21808955 is an apocalyptic number.

21808955 is a deficient number, since it is larger than the sum of its proper divisors (8903077).

21808955 is an equidigital number, since it uses as much as digits as its factorization.

21808955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 435 (or 392 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 21808955 is about 4670.0058886473. The cubic root of 21808955 is about 279.3904896429.

The spelling of 21808955 in words is "twenty-one million, eight hundred eight thousand, nine hundred fifty-five".