21590399 has 4 divisors (see below), whose sum is σ = 22529136. Its totient is φ = 20651664.

The previous prime is 21590369. The next prime is 21590411. The reversal of 21590399 is 99309512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21590399 - 2²⁴ = 4813183 is a prime.

It is a super-2 number, since 2×21590399² = 932290657958402, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21590329) 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, 469334 + ... + 469379.

It is an arithmetic number, because the mean of its divisors is an integer number (5632284).

Almost surely, 2^21590399 is an apocalyptic number.

21590399 is a deficient number, since it is larger than the sum of its proper divisors (938737).

21590399 is an equidigital number, since it uses as much as digits as its factorization.

21590399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 938736.

The product of its (nonzero) digits is 21870, while the sum is 38.

The square root of 21590399 is about 4646.5469975026. The cubic root of 21590399 is about 278.4540610364.

The spelling of 21590399 in words is "twenty-one million, five hundred ninety thousand, three hundred ninety-nine".