21925217 has 4 divisors (see below), whose sum is σ = 21934596. Its totient is φ = 21915840.

The previous prime is 21925159. The next prime is 21925219. The reversal of 21925217 is 71252912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8994001 + 12931216 = 2999^2 + 3596^2 .

It is a cyclic number.

It is not a de Polignac number, because 21925217 - 2⁸ = 21924961 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21925217.

It is not an unprimeable number, because it can be changed into a prime (21925219) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1973 + ... + 6909.

It is an arithmetic number, because the mean of its divisors is an integer number (5483649).

Almost surely, 2^21925217 is an apocalyptic number.

It is an amenable number.

21925217 is a deficient number, since it is larger than the sum of its proper divisors (9379).

21925217 is an equidigital number, since it uses as much as digits as its factorization.

21925217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9378.

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

The square root of 21925217 is about 4682.4370791288. The cubic root of 21925217 is about 279.8860803581.

The spelling of 21925217 in words is "twenty-one million, nine hundred twenty-five thousand, two hundred seventeen".