21106979 has 4 divisors (see below), whose sum is σ = 22348584. Its totient is φ = 19865376.

The previous prime is 21106961. The next prime is 21106993. The reversal of 21106979 is 97960112.

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

It is a cyclic number.

It is not a de Polignac number, because 21106979 - 2¹² = 21102883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21106079) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 620777 + ... + 620810.

It is an arithmetic number, because the mean of its divisors is an integer number (5587146).

Almost surely, 2^21106979 is an apocalyptic number.

21106979 is a deficient number, since it is larger than the sum of its proper divisors (1241605).

21106979 is a wasteful number, since it uses less digits than its factorization.

21106979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1241604.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 21106979 is about 4594.2332330869. The cubic root of 21106979 is about 276.3601115748.

The spelling of 21106979 in words is "twenty-one million, one hundred six thousand, nine hundred seventy-nine".