101999 has 2 divisors, whose sum is σ = 102000. Its totient is φ = 101998.

The previous prime is 101987. The next prime is 102001. The reversal of 101999 is 999101.

It is a strong prime.

It is an emirp because it is prime and its reverse (999101) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-101999 is a prime.

It is a Sophie Germain prime.

Together with 102001, it forms a pair of twin primes.

It is a Chen prime.

101999 is a modest number, since divided by 999 gives 101 as remainder.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (101929) 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, 50999 + 51000.

It is an arithmetic number, because the mean of its divisors is an integer number (51000).

2¹⁰¹⁹⁹⁹ is an apocalyptic number.

101999 is a deficient number, since it is larger than the sum of its proper divisors (1).

101999 is an equidigital number, since it uses as much as digits as its factorization.

101999 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 729, while the sum is 29.

The square root of 101999 is about 319.3728228889. The cubic root of 101999 is about 46.7231345926.

The spelling of 101999 in words is "one hundred one thousand, nine hundred ninety-nine".