21905597 has 6 divisors (see below), whose sum is σ = 25482078. Its totient is φ = 18776184.

The previous prime is 21905593. The next prime is 21905617. The reversal of 21905597 is 79550912.

It can be written as a sum of positive squares in only one way, i.e., 14182756 + 7722841 = 3766^2 + 2779^2 .

It is not a de Polignac number, because 21905597 - 2² = 21905593 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 21905597.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21905593) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 223478 + ... + 223575.

It is an arithmetic number, because the mean of its divisors is an integer number (4247013).

Almost surely, 2^21905597 is an apocalyptic number.

It is an amenable number.

21905597 is a deficient number, since it is larger than the sum of its proper divisors (3576481).

21905597 is an equidigital number, since it uses as much as digits as its factorization.

21905597 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 447067 (or 447060 counting only the distinct ones).

The product of its (nonzero) digits is 28350, while the sum is 38.

The square root of 21905597 is about 4680.3415473660. The cubic root of 21905597 is about 279.8025691556.

The spelling of 21905597 in words is "twenty-one million, nine hundred five thousand, five hundred ninety-seven".