21251188 has 12 divisors (see below), whose sum is σ = 42502432. Its totient is φ = 9107640.

The previous prime is 21251179. The next prime is 21251201. The reversal of 21251188 is 88115212.

21251188 is an admirable number.

It is a super-2 number, since 2×21251188² = 903225982822688, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28), and also a Moran number because the ratio is a prime number: 758971 = 21251188 / (2 + 1 + 2 + 5 + 1 + 1 + 8 + 8).

It is a congruent 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, 379458 + ... + 379513.

Almost surely, 2^21251188 is an apocalyptic number.

21251188 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21251188 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.

21251188 is a wasteful number, since it uses less digits than its factorization.

21251188 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 758982 (or 758980 counting only the distinct ones).

The product of its digits is 1280, while the sum is 28.

The square root of 21251188 is about 4609.9010835375. The cubic root of 21251188 is about 276.9880743996.

The spelling of 21251188 in words is "twenty-one million, two hundred fifty-one thousand, one hundred eighty-eight".