1205138979 has 30 divisors (see below), whose sum is σ = 1965620316. Its totient is φ = 729759240.

The previous prime is 1205138923. The next prime is 1205138999. The reversal of 1205138979 is 9798315021.

1205138979 is a `hidden beast` number, since 120 + 513 + 8 + 9 + 7 + 9 = 666.

It is not a de Polignac number, because 1205138979 - 2²³ = 1196750371 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1205138999) 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 29 ways as a sum of consecutive naturals, for example, 1035652 + ... + 1036814.

Almost surely, 2^1205138979 is an apocalyptic number.

1205138979 is a deficient number, since it is larger than the sum of its proper divisors (760481337).

1205138979 is an frugal number, since it uses more digits than its factorization.

1205138979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2349 (or 1177 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The square root of 1205138979 is about 34715.1116806500. Note that the first 3 decimals coincide. The cubic root of 1205138979 is about 1064.1733478070.

The spelling of 1205138979 in words is "one billion, two hundred five million, one hundred thirty-eight thousand, nine hundred seventy-nine".