21109979 has 8 divisors (see below), whose sum is σ = 23164272. Its totient is φ = 19078240.

The previous prime is 21109973. The next prime is 21109987. The reversal of 21109979 is 97990112.

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

It is a cyclic number.

It is not a de Polignac number, because 21109979 - 2²⁰ = 20061403 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21109973) 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, 3644 + ... + 7449.

It is an arithmetic number, because the mean of its divisors is an integer number (2895534).

Almost surely, 2^21109979 is an apocalyptic number.

21109979 is a deficient number, since it is larger than the sum of its proper divisors (2054293).

21109979 is a wasteful number, since it uses less digits than its factorization.

21109979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11277.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 21109979 is about 4594.5597177532. The cubic root of 21109979 is about 276.3732042595.

The spelling of 21109979 in words is "twenty-one million, one hundred nine thousand, nine hundred seventy-nine".