21921275 has 6 divisors (see below), whose sum is σ = 27182412. Its totient is φ = 17537000.

The previous prime is 21921259. The next prime is 21921281. The reversal of 21921275 is 57212912.

It is not a de Polignac number, because 21921275 - 2⁴ = 21921259 is a prime.

It is a Duffinian 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, 438401 + ... + 438450.

It is an arithmetic number, because the mean of its divisors is an integer number (4530402).

Almost surely, 2^21921275 is an apocalyptic number.

21921275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21921275 is a deficient number, since it is larger than the sum of its proper divisors (5261137).

21921275 is an equidigital number, since it uses as much as digits as its factorization.

21921275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 876861 (or 876856 counting only the distinct ones).

The product of its digits is 2520, while the sum is 29.

The square root of 21921275 is about 4682.0161255596. The cubic root of 21921275 is about 279.8693055023.

The spelling of 21921275 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred seventy-five".