21373221 has 12 divisors (see below), whose sum is σ = 28884128. Its totient is φ = 14056824.

The previous prime is 21373207. The next prime is 21373223. The reversal of 21373221 is 12237312.

It is not a de Polignac number, because 21373221 - 2²³ = 12984613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21373223) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 81136 + ... + 81398.

Almost surely, 2^21373221 is an apocalyptic number.

It is an amenable number.

21373221 is a deficient number, since it is larger than the sum of its proper divisors (7510907).

21373221 is an equidigital number, since it uses as much as digits as its factorization.

21373221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 632 (or 369 counting only the distinct ones).

The product of its digits is 504, while the sum is 21.

The square root of 21373221 is about 4623.1181036179. The cubic root of 21373221 is about 277.5172556432.

The spelling of 21373221 in words is "twenty-one million, three hundred seventy-three thousand, two hundred twenty-one".