135999 has 20 divisors (see below), whose sum is σ = 214896. Its totient is φ = 85536.

The previous prime is 135979. The next prime is 136013. The reversal of 135999 is 999531.

It is not a de Polignac number, because 135999 - 2⁸ = 135743 is a prime.

135999 is a modest number, since divided by 999 gives 135 as remainder.

It is a plaindrome in base 10.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 135999.

It is not an unprimeable number, because it can be changed into a prime (135929) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1827 + ... + 1899.

2¹³⁵⁹⁹⁹ is an apocalyptic number.

135999 is a deficient number, since it is larger than the sum of its proper divisors (78897).

135999 is an equidigital number, since it uses as much as digits as its factorization.

135999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108 (or 99 counting only the distinct ones).

The product of its digits is 10935, while the sum is 36.

The square root of 135999 is about 368.7804224739. The cubic root of 135999 is about 51.4255057696.

The spelling of 135999 in words is "one hundred thirty-five thousand, nine hundred ninety-nine".