199791997 has 2 divisors, whose sum is σ = 199791998. Its totient is φ = 199791996.

The previous prime is 199791983. The next prime is 199792009. The reversal of 199791997 is 799197991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 197514916 + 2277081 = 14054^2 + 1509^2 .

It is an emirp because it is prime and its reverse (799197991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199791997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199792997) 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, 99895998 + 99895999.

It is an arithmetic number, because the mean of its divisors is an integer number (99895999).

Almost surely, 2^199791997 is an apocalyptic number.

It is an amenable number.

199791997 is a deficient number, since it is larger than the sum of its proper divisors (1).

199791997 is an equidigital number, since it uses as much as digits as its factorization.

199791997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2893401, while the sum is 61.

The square root of 199791997 is about 14134.7796940738. The cubic root of 199791997 is about 584.6007424990.

The spelling of 199791997 in words is "one hundred ninety-nine million, seven hundred ninety-one thousand, nine hundred ninety-seven".