21255553 has 16 divisors (see below), whose sum is σ = 24256512. Its totient is φ = 18450000.

The previous prime is 21255541. The next prime is 21255557. The reversal of 21255553 is 35555212.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21255553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27928 + ... + 28678.

It is an arithmetic number, because the mean of its divisors is an integer number (1516032).

Almost surely, 2^21255553 is an apocalyptic number.

It is an amenable number.

21255553 is a deficient number, since it is larger than the sum of its proper divisors (3000959).

21255553 is a wasteful number, since it uses less digits than its factorization.

21255553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 876.

The product of its digits is 7500, while the sum is 28.

The square root of 21255553 is about 4610.3744967193. The cubic root of 21255553 is about 277.0070375775.

The spelling of 21255553 in words is "twenty-one million, two hundred fifty-five thousand, five hundred fifty-three".