21117875 has 8 divisors (see below), whose sum is σ = 26355264. Its totient is φ = 16894200.

The previous prime is 21117871. The next prime is 21117881. The reversal of 21117875 is 57871112.

It is not a de Polignac number, because 21117875 - 2² = 21117871 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21117871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 84347 + ... + 84596.

It is an arithmetic number, because the mean of its divisors is an integer number (3294408).

Almost surely, 2^21117875 is an apocalyptic number.

21117875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21117875 is a deficient number, since it is larger than the sum of its proper divisors (5237389).

21117875 is an equidigital number, since it uses as much as digits as its factorization.

21117875 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168958 (or 168948 counting only the distinct ones).

The product of its digits is 3920, while the sum is 32.

The square root of 21117875 is about 4595.4189145278. The cubic root of 21117875 is about 276.4076582775.

Adding to 21117875 its reverse (57871112), we get a palindrome (78988987).

The spelling of 21117875 in words is "twenty-one million, one hundred seventeen thousand, eight hundred seventy-five".