21457228 has 12 divisors (see below), whose sum is σ = 40438720. Its totient is φ = 9903312.

The previous prime is 21457207. The next prime is 21457253. The reversal of 21457228 is 82275412.

It is a happy number.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21457228.

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, 206268 + ... + 206371.

Almost surely, 2^21457228 is an apocalyptic number.

It is an amenable number.

21457228 is a deficient number, since it is larger than the sum of its proper divisors (18981492).

21457228 is a wasteful number, since it uses less digits than its factorization.

21457228 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 412656 (or 412654 counting only the distinct ones).

The product of its digits is 8960, while the sum is 31.

The square root of 21457228 is about 4632.1947282039. The cubic root of 21457228 is about 277.8803722483.

The spelling of 21457228 in words is "twenty-one million, four hundred fifty-seven thousand, two hundred twenty-eight".