21197975 has 6 divisors (see below), whose sum is σ = 26285520. Its totient is φ = 16958360.

The previous prime is 21197947. The next prime is 21197989. The reversal of 21197975 is 57979112.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21197975 is a prime.

It is a congruent number.

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 423935 + ... + 423984.

It is an arithmetic number, because the mean of its divisors is an integer number (4380920).

Almost surely, 2^21197975 is an apocalyptic number.

21197975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21197975 is a deficient number, since it is larger than the sum of its proper divisors (5087545).

21197975 is an equidigital number, since it uses as much as digits as its factorization.

21197975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 847929 (or 847924 counting only the distinct ones).

The product of its digits is 39690, while the sum is 41.

The square root of 21197975 is about 4604.1258670892. The cubic root of 21197975 is about 276.7566883392.

The spelling of 21197975 in words is "twenty-one million, one hundred ninety-seven thousand, nine hundred seventy-five".