128377991 has 12 divisors (see below), whose sum is σ = 149534712. Its totient is φ = 109893168.

The previous prime is 128377979. The next prime is 128378017. The reversal of 128377991 is 199773821.

It is a de Polignac number, because none of the positive numbers 2^k-128377991 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 (128373991) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 53861 + ... + 56193.

It is an arithmetic number, because the mean of its divisors is an integer number (12461226).

Almost surely, 2^128377991 is an apocalyptic number.

128377991 is a deficient number, since it is larger than the sum of its proper divisors (21156721).

128377991 is a wasteful number, since it uses less digits than its factorization.

128377991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3470 (or 3463 counting only the distinct ones).

The product of its digits is 190512, while the sum is 47.

The square root of 128377991 is about 11330.4011844241. The cubic root of 128377991 is about 504.4640145399.

The spelling of 128377991 in words is "one hundred twenty-eight million, three hundred seventy-seven thousand, nine hundred ninety-one".