198021979 has 2 divisors, whose sum is σ = 198021980. Its totient is φ = 198021978.

The previous prime is 198021977. The next prime is 198022003. The reversal of 198021979 is 979120891.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 198021979 - 2¹ = 198021977 is a prime.

Together with 198021977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (198021977) 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 as a sum of consecutive naturals, namely, 99010989 + 99010990.

It is an arithmetic number, because the mean of its divisors is an integer number (99010990).

Almost surely, 2^198021979 is an apocalyptic number.

198021979 is a deficient number, since it is larger than the sum of its proper divisors (1).

198021979 is an equidigital number, since it uses as much as digits as its factorization.

198021979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81648, while the sum is 46.

The square root of 198021979 is about 14072.0282475555. The cubic root of 198021979 is about 582.8692338722.

The spelling of 198021979 in words is "one hundred ninety-eight million, twenty-one thousand, nine hundred seventy-nine".