21408955 has 4 divisors (see below), whose sum is σ = 25690752. Its totient is φ = 17127160.

The previous prime is 21408949. The next prime is 21408971. The reversal of 21408955 is 55980412.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21408955 - 2²³ = 13020347 is a prime.

It is a super-3 number, since 3×21408955³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21408955.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2140891 + ... + 2140900.

It is an arithmetic number, because the mean of its divisors is an integer number (6422688).

Almost surely, 2^21408955 is an apocalyptic number.

21408955 is a deficient number, since it is larger than the sum of its proper divisors (4281797).

21408955 is an equidigital number, since it uses as much as digits as its factorization.

21408955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4281796.

The product of its (nonzero) digits is 14400, while the sum is 34.

The square root of 21408955 is about 4626.9811972819. The cubic root of 21408955 is about 277.6718303809.

The spelling of 21408955 in words is "twenty-one million, four hundred eight thousand, nine hundred fifty-five".