161999 has 2 divisors, whose sum is σ = 162000. Its totient is φ = 161998.

The previous prime is 161983. The next prime is 162007. The reversal of 161999 is 999161.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 161999 - 2⁴ = 161983 is a prime.

It is a Chen prime.

161999 is a modest number, since divided by 999 gives 161 as remainder.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161969) 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, 80999 + 81000.

It is an arithmetic number, because the mean of its divisors is an integer number (81000).

2¹⁶¹⁹⁹⁹ is an apocalyptic number.

161999 is a deficient number, since it is larger than the sum of its proper divisors (1).

161999 is an equidigital number, since it uses as much as digits as its factorization.

161999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4374, while the sum is 35.

The square root of 161999 is about 402.4909936881. The cubic root of 161999 is about 54.5135056168.

The spelling of 161999 in words is "one hundred sixty-one thousand, nine hundred ninety-nine".