128999 has 4 divisors (see below), whose sum is σ = 138936. Its totient is φ = 119064.

The previous prime is 128993. The next prime is 129001. The reversal of 128999 is 999821.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 128999 - 2⁴ = 128983 is a prime.

It is a Duffinian number.

128999 is a modest number, since divided by 999 gives 128 as remainder.

It is a plaindrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4949 + ... + 4974.

It is an arithmetic number, because the mean of its divisors is an integer number (34734).

2¹²⁸⁹⁹⁹ is an apocalyptic number.

128999 is a deficient number, since it is larger than the sum of its proper divisors (9937).

128999 is an equidigital number, since it uses as much as digits as its factorization.

128999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9936.

The product of its digits is 11664, while the sum is 38.

The square root of 128999 is about 359.1643078035. The cubic root of 128999 is about 50.5276129091.

The spelling of 128999 in words is "one hundred twenty-eight thousand, nine hundred ninety-nine".