21278975 has 6 divisors (see below), whose sum is σ = 26385960. Its totient is φ = 17023160.

The previous prime is 21278963. The next prime is 21278981. The reversal of 21278975 is 57987212.

It is not a de Polignac number, because 21278975 - 2⁶ = 21278911 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 425555 + ... + 425604.

It is an arithmetic number, because the mean of its divisors is an integer number (4397660).

Almost surely, 2^21278975 is an apocalyptic number.

21278975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21278975 is a deficient number, since it is larger than the sum of its proper divisors (5106985).

21278975 is an equidigital number, since it uses as much as digits as its factorization.

21278975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 851169 (or 851164 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 21278975 is about 4612.9139380656. The cubic root of 21278975 is about 277.1087471115.

The spelling of 21278975 in words is "twenty-one million, two hundred seventy-eight thousand, nine hundred seventy-five".