21255321 has 16 divisors (see below), whose sum is σ = 30110400. Its totient is φ = 13291008.

The previous prime is 21255317. The next prime is 21255323. The reversal of 21255321 is 12355212.

It is not a de Polignac number, because 21255321 - 2² = 21255317 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21255323) 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, 20350 + ... + 21368.

It is an arithmetic number, because the mean of its divisors is an integer number (1881900).

Almost surely, 2^21255321 is an apocalyptic number.

It is an amenable number.

21255321 is a deficient number, since it is larger than the sum of its proper divisors (8855079).

21255321 is a wasteful number, since it uses less digits than its factorization.

21255321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1448.

The product of its digits is 600, while the sum is 21.

The square root of 21255321 is about 4610.3493360048. The cubic root of 21255321 is about 277.0060297488.

The spelling of 21255321 in words is "twenty-one million, two hundred fifty-five thousand, three hundred twenty-one".