21305875 has 8 divisors (see below), whose sum is σ = 26589888. Its totient is φ = 17044600.

The previous prime is 21305857. The next prime is 21305891. The reversal of 21305875 is 57850312.

It is not a de Polignac number, because 21305875 - 2¹⁵ = 21273107 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 85099 + ... + 85348.

It is an arithmetic number, because the mean of its divisors is an integer number (3323736).

Almost surely, 2^21305875 is an apocalyptic number.

21305875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21305875 is a deficient number, since it is larger than the sum of its proper divisors (5284013).

21305875 is an equidigital number, since it uses as much as digits as its factorization.

21305875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 170462 (or 170452 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21305875 is about 4615.8287446568. The cubic root of 21305875 is about 277.2254677461.

The spelling of 21305875 in words is "twenty-one million, three hundred five thousand, eight hundred seventy-five".