21157828 has 12 divisors (see below), whose sum is σ = 37093392. Its totient is φ = 10559720.

The previous prime is 21157817. The next prime is 21157831. The reversal of 21157828 is 82875112.

It is a junction number, because it is equal to n+sod(n) for n = 21157793 and 21157802.

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, 2158 + ... + 6853.

It is an arithmetic number, because the mean of its divisors is an integer number (3091116).

Almost surely, 2^21157828 is an apocalyptic number.

It is an amenable number.

21157828 is a deficient number, since it is larger than the sum of its proper divisors (15935564).

21157828 is a wasteful number, since it uses less digits than its factorization.

21157828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9602 (or 9600 counting only the distinct ones).

The product of its digits is 8960, while the sum is 34.

The square root of 21157828 is about 4599.7639069848. The cubic root of 21157828 is about 276.5818607511.

The spelling of 21157828 in words is "twenty-one million, one hundred fifty-seven thousand, eight hundred twenty-eight".