21512428 has 12 divisors (see below), whose sum is σ = 43024912. Its totient is φ = 9219600.

The previous prime is 21512401. The next prime is 21512431. The reversal of 21512428 is 82421512.

21512428 is an admirable number.

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, 384123 + ... + 384178.

Almost surely, 2^21512428 is an apocalyptic number.

21512428 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21512428 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21512428 is a wasteful number, since it uses less digits than its factorization.

21512428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 768312 (or 768310 counting only the distinct ones).

The product of its digits is 1280, while the sum is 25.

The square root of 21512428 is about 4638.1491998425. The cubic root of 21512428 is about 278.1184561521.

The spelling of 21512428 in words is "twenty-one million, five hundred twelve thousand, four hundred twenty-eight".