20909979 has 6 divisors (see below), whose sum is σ = 30203316. Its totient is φ = 13939980.

The previous prime is 20909969. The next prime is 20909981. The reversal of 20909979 is 97990902.

It is not a de Polignac number, because 20909979 - 2⁵ = 20909947 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20909939) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1161657 + ... + 1161674.

It is an arithmetic number, because the mean of its divisors is an integer number (5033886).

Almost surely, 2^20909979 is an apocalyptic number.

20909979 is a deficient number, since it is larger than the sum of its proper divisors (9293337).

20909979 is a wasteful number, since it uses less digits than its factorization.

20909979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2323337 (or 2323334 counting only the distinct ones).

The product of its (nonzero) digits is 91854, while the sum is 45.

The square root of 20909979 is about 4572.7430498553. The cubic root of 20909979 is about 275.4976289949.

The spelling of 20909979 in words is "twenty million, nine hundred nine thousand, nine hundred seventy-nine".