171999979 has 2 divisors, whose sum is σ = 171999980. Its totient is φ = 171999978.

The previous prime is 171999977. The next prime is 171999983. The reversal of 171999979 is 979999171.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 171999979 - 2¹ = 171999977 is a prime.

Together with 171999977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (171999973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85999989 + 85999990.

It is an arithmetic number, because the mean of its divisors is an integer number (85999990).

Almost surely, 2^171999979 is an apocalyptic number.

171999979 is a deficient number, since it is larger than the sum of its proper divisors (1).

171999979 is an equidigital number, since it uses as much as digits as its factorization.

171999979 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 171999979 is about 13114.8762479865. The cubic root of 171999979 is about 556.1297540189.

The spelling of 171999979 in words is "one hundred seventy-one million, nine hundred ninety-nine thousand, nine hundred seventy-nine".