399999979 has 4 divisors (see below), whose sum is σ = 400122976. Its totient is φ = 399876984.

The previous prime is 399999959. The next prime is 400000009. The reversal of 399999979 is 979999993.

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 399999979 - 2⁵ = 399999947 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399999949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 56484 + ... + 63169.

It is an arithmetic number, because the mean of its divisors is an integer number (100030744).

Almost surely, 2^399999979 is an apocalyptic number.

399999979 is a deficient number, since it is larger than the sum of its proper divisors (122997).

399999979 is a wasteful number, since it uses less digits than its factorization.

399999979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 122996.

The product of its digits is 100442349, while the sum is 73.

The square root of 399999979 is about 19999.9994750000. Note that the first 3 decimals coincide. The cubic root of 399999979 is about 736.8062868340.

The spelling of 399999979 in words is "three hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred seventy-nine".