19999979 has 4 divisors (see below), whose sum is σ = 20010984. Its totient is φ = 19988976.

The previous prime is 19999963. The next prime is 19999981. The reversal of 19999979 is 97999991.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 97999991 = 6199 ⋅15809.

It is a cyclic number.

It is not a de Polignac number, because 19999979 - 2⁴ = 19999963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19999909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2057 + ... + 6650.

It is an arithmetic number, because the mean of its divisors is an integer number (5002746).

Almost surely, 2^19999979 is an apocalyptic number.

19999979 is a deficient number, since it is larger than the sum of its proper divisors (11005).

19999979 is an equidigital number, since it uses as much as digits as its factorization.

19999979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11004.

The product of its digits is 3720087, while the sum is 62.

The square root of 19999979 is about 4472.1336071276. The cubic root of 19999979 is about 271.4416666548.

The spelling of 19999979 in words is "nineteen million, nine hundred ninety-nine thousand, nine hundred seventy-nine".