21807399 has 4 divisors (see below), whose sum is σ = 29076536. Its totient is φ = 14538264.

The previous prime is 21807377. The next prime is 21807419. The reversal of 21807399 is 99370812.

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

It is not a de Polignac number, because 21807399 - 2⁷ = 21807271 is a prime.

It is a super-2 number, since 2×21807399² = 951125302290402, 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 (21877399) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3634564 + ... + 3634569.

It is an arithmetic number, because the mean of its divisors is an integer number (7269134).

Almost surely, 2^21807399 is an apocalyptic number.

21807399 is a deficient number, since it is larger than the sum of its proper divisors (7269137).

21807399 is an equidigital number, since it uses as much as digits as its factorization.

21807399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7269136.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21807399 is about 4669.8392905966. The cubic root of 21807399 is about 279.3838449422.

The spelling of 21807399 in words is "twenty-one million, eight hundred seven thousand, three hundred ninety-nine".