20209979 has 4 divisors (see below), whose sum is σ = 20226600. Its totient is φ = 20193360.

The previous prime is 20209967. The next prime is 20209993. The reversal of 20209979 is 97990202.

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 20209979 - 2⁴ = 20209963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20209909) 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, 6329 + ... + 8970.

It is an arithmetic number, because the mean of its divisors is an integer number (5056650).

Almost surely, 2^20209979 is an apocalyptic number.

20209979 is a deficient number, since it is larger than the sum of its proper divisors (16621).

20209979 is a wasteful number, since it uses less digits than its factorization.

20209979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16620.

The product of its (nonzero) digits is 20412, while the sum is 38.

The square root of 20209979 is about 4495.5510229559. The cubic root of 20209979 is about 272.3884075804.

The spelling of 20209979 in words is "twenty million, two hundred nine thousand, nine hundred seventy-nine".