128117989 has 4 divisors (see below), whose sum is σ = 131242860. Its totient is φ = 124993120.

The previous prime is 128117987. The next prime is 128117999. The reversal of 128117989 is 989711821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 989711821 = 7 ⋅141387403.

It can be written as a sum of positive squares in 2 ways, for example, as 71115489 + 57002500 = 8433^2 + 7550^2 .

It is a cyclic number.

It is not a de Polignac number, because 128117989 - 2¹ = 128117987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128117987) 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, 1562374 + ... + 1562455.

It is an arithmetic number, because the mean of its divisors is an integer number (32810715).

Almost surely, 2^128117989 is an apocalyptic number.

It is an amenable number.

128117989 is a deficient number, since it is larger than the sum of its proper divisors (3124871).

128117989 is an equidigital number, since it uses as much as digits as its factorization.

128117989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3124870.

The product of its digits is 72576, while the sum is 46.

The square root of 128117989 is about 11318.9217242633. The cubic root of 128117989 is about 504.1232232615.

The spelling of 128117989 in words is "one hundred twenty-eight million, one hundred seventeen thousand, nine hundred eighty-nine".