20405979 has 32 divisors (see below), whose sum is σ = 33300480. Its totient is φ = 12247200.

The previous prime is 20405977. The next prime is 20405993. The reversal of 20405979 is 97950402.

20405979 is a `hidden beast` number, since 20 + 40 + 597 + 9 = 666.

It is not a de Polignac number, because 20405979 - 2¹ = 20405977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20405977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 37449 + ... + 37989.

It is an arithmetic number, because the mean of its divisors is an integer number (1040640).

Almost surely, 2^20405979 is an apocalyptic number.

20405979 is a deficient number, since it is larger than the sum of its proper divisors (12894501).

20405979 is a wasteful number, since it uses less digits than its factorization.

20405979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 688 (or 682 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 20405979 is about 4517.2977541889. The cubic root of 20405979 is about 273.2661334238.

The spelling of 20405979 in words is "twenty million, four hundred five thousand, nine hundred seventy-nine".