21608979 has 8 divisors (see below), whose sum is σ = 32928000. Its totient is φ = 12347976.

The previous prime is 21608969. The next prime is 21608987. The reversal of 21608979 is 97980612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21608979 - 2⁴ = 21608963 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21608979.

It is not an unprimeable number, because it can be changed into a prime (21608929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 514479 + ... + 514520.

It is an arithmetic number, because the mean of its divisors is an integer number (4116000).

Almost surely, 2^21608979 is an apocalyptic number.

21608979 is a deficient number, since it is larger than the sum of its proper divisors (11319021).

21608979 is a wasteful number, since it uses less digits than its factorization.

21608979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1029009.

The product of its (nonzero) digits is 54432, while the sum is 42.

The square root of 21608979 is about 4648.5459016772. The cubic root of 21608979 is about 278.5339143247.

The spelling of 21608979 in words is "twenty-one million, six hundred eight thousand, nine hundred seventy-nine".