21608609 has 4 divisors (see below), whose sum is σ = 23573040. Its totient is φ = 19644180.

The previous prime is 21608603. The next prime is 21608611. The reversal of 21608609 is 90680612.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21608609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21608603) 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, 982199 + ... + 982220.

It is an arithmetic number, because the mean of its divisors is an integer number (5893260).

Almost surely, 2^21608609 is an apocalyptic number.

It is an amenable number.

21608609 is a deficient number, since it is larger than the sum of its proper divisors (1964431).

21608609 is a wasteful number, since it uses less digits than its factorization.

21608609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1964430.

The product of its (nonzero) digits is 5184, while the sum is 32.

The square root of 21608609 is about 4648.5061041156. The cubic root of 21608609 is about 278.5323245822.

The spelling of 21608609 in words is "twenty-one million, six hundred eight thousand, six hundred nine".