21994979 has 4 divisors (see below), whose sum is σ = 22060584. Its totient is φ = 21929376.

The previous prime is 21994897. The next prime is 21994981. The reversal of 21994979 is 97949912.

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 21994979 - 2¹⁶ = 21929443 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21996979) 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, 32297 + ... + 32970.

It is an arithmetic number, because the mean of its divisors is an integer number (5515146).

Almost surely, 2^21994979 is an apocalyptic number.

21994979 is a deficient number, since it is larger than the sum of its proper divisors (65605).

21994979 is an equidigital number, since it uses as much as digits as its factorization.

21994979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65604.

The product of its digits is 367416, while the sum is 50.

The square root of 21994979 is about 4689.8804888824. The cubic root of 21994979 is about 280.1826147172.

The spelling of 21994979 in words is "twenty-one million, nine hundred ninety-four thousand, nine hundred seventy-nine".