21255331 has 4 divisors (see below), whose sum is σ = 21297600. Its totient is φ = 21213064.

The previous prime is 21255329. The next prime is 21255361. The reversal of 21255331 is 13355212.

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

It is a cyclic number.

It is not a de Polignac number, because 21255331 - 2¹ = 21255329 is a prime.

It is a super-2 number, since 2×21255331² = 903578191839122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20371 + ... + 21388.

It is an arithmetic number, because the mean of its divisors is an integer number (5324400).

Almost surely, 2^21255331 is an apocalyptic number.

21255331 is a deficient number, since it is larger than the sum of its proper divisors (42269).

21255331 is an equidigital number, since it uses as much as digits as its factorization.

21255331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42268.

The product of its digits is 900, while the sum is 22.

The square root of 21255331 is about 4610.3504205212. The cubic root of 21255331 is about 277.0060731898.

The spelling of 21255331 in words is "twenty-one million, two hundred fifty-five thousand, three hundred thirty-one".