21908389 has 4 divisors (see below), whose sum is σ = 22081024. Its totient is φ = 21735756.

The previous prime is 21908377. The next prime is 21908401. The reversal of 21908389 is 98380912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21908377) and next prime (21908401).

It is a cyclic number.

It is not a de Polignac number, because 21908389 - 2⁷ = 21908261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21908989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86127 + ... + 86380.

It is an arithmetic number, because the mean of its divisors is an integer number (5520256).

Almost surely, 2^21908389 is an apocalyptic number.

It is an amenable number.

21908389 is a deficient number, since it is larger than the sum of its proper divisors (172635).

21908389 is a wasteful number, since it uses less digits than its factorization.

21908389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172634.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 21908389 is about 4680.6398066931. The cubic root of 21908389 is about 279.8144561569.

The spelling of 21908389 in words is "twenty-one million, nine hundred eight thousand, three hundred eighty-nine".