21257375 has 16 divisors (see below), whose sum is σ = 26709696. Its totient is φ = 16890400.

The previous prime is 21257347. The next prime is 21257407. The reversal of 21257375 is 57375212.

It is not a de Polignac number, because 21257375 - 2¹² = 21253279 is a prime.

It is a Duffinian number.

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 15 ways as a sum of consecutive naturals, for example, 21134 + ... + 22116.

It is an arithmetic number, because the mean of its divisors is an integer number (1669356).

Almost surely, 2^21257375 is an apocalyptic number.

21257375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21257375 is a deficient number, since it is larger than the sum of its proper divisors (5452321).

21257375 is an equidigital number, since it uses as much as digits as its factorization.

21257375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1171 (or 1161 counting only the distinct ones).

The product of its digits is 14700, while the sum is 32.

The square root of 21257375 is about 4610.5720903159. The cubic root of 21257375 is about 277.0149522528.

The spelling of 21257375 in words is "twenty-one million, two hundred fifty-seven thousand, three hundred seventy-five".