19979 has 2 divisors, whose sum is σ = 19980. Its totient is φ = 19978.

The previous prime is 19973. The next prime is 19991. The reversal of 19979 is 97991.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19979 - 2⁴ = 19963 is a prime.

It is not a weakly prime, because it can be changed into another prime (19973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9989 + 9990.

It is an arithmetic number, because the mean of its divisors is an integer number (9990).

2¹⁹⁹⁷⁹ is an apocalyptic number.

19979 is a deficient number, since it is larger than the sum of its proper divisors (1).

19979 is an equidigital number, since it uses as much as digits as its factorization.

19979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5103, while the sum is 35.

The square root of 19979 is about 141.3470905254. The cubic root of 19979 is about 27.1346723772.

The spelling of 19979 in words is "nineteen thousand, nine hundred seventy-nine".