21151875 has 40 divisors (see below), whose sum is σ = 36550800. Its totient is φ = 10864000.

The previous prime is 21151873. The next prime is 21151877. The reversal of 21151875 is 57815112.

It is an interprime number because it is at equal distance from previous prime (21151873) and next prime (21151877).

It is not a de Polignac number, because 21151875 - 2¹ = 21151873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21151873) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 54181 + ... + 54569.

It is an arithmetic number, because the mean of its divisors is an integer number (913770).

Almost surely, 2^21151875 is an apocalyptic number.

21151875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21151875 is a deficient number, since it is larger than the sum of its proper divisors (15398925).

21151875 is an equidigital number, since it uses as much as digits as its factorization.

21151875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441 (or 426 counting only the distinct ones).

The product of its digits is 2800, while the sum is 30.

The square root of 21151875 is about 4599.1167630318. The cubic root of 21151875 is about 276.5559184811. Note that the first 3 decimals are identical.

Adding to 21151875 its reverse (57815112), we get a palindrome (78966987).

The spelling of 21151875 in words is "twenty-one million, one hundred fifty-one thousand, eight hundred seventy-five".