128097991 has 8 divisors (see below), whose sum is σ = 148403744. Its totient is φ = 108293760.

The previous prime is 128097961. The next prime is 128098001. The reversal of 128097991 is 199790821.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128097991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128097961) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 124830 + ... + 125851.

It is an arithmetic number, because the mean of its divisors is an integer number (18550468).

Almost surely, 2^128097991 is an apocalyptic number.

128097991 is a deficient number, since it is larger than the sum of its proper divisors (20305753).

128097991 is an equidigital number, since it uses as much as digits as its factorization.

128097991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 250761.

The product of its (nonzero) digits is 81648, while the sum is 46.

The square root of 128097991 is about 11318.0383017553. The cubic root of 128097991 is about 504.0969922826.

The spelling of 128097991 in words is "one hundred twenty-eight million, ninety-seven thousand, nine hundred ninety-one".