128042991 has 16 divisors (see below), whose sum is σ = 189995520. Its totient is φ = 85226040.

The previous prime is 128042987. The next prime is 128043011. The reversal of 128042991 is 199240821.

It is not a de Polignac number, because 128042991 - 2² = 128042987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128042591) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15226 + ... + 22088.

It is an arithmetic number, because the mean of its divisors is an integer number (11874720).

Almost surely, 2^128042991 is an apocalyptic number.

128042991 is a deficient number, since it is larger than the sum of its proper divisors (61952529).

128042991 is an equidigital number, since it uses as much as digits as its factorization.

128042991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7563 (or 7557 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 128042991 is about 11315.6082912056. The cubic root of 128042991 is about 504.0248357943.

The spelling of 128042991 in words is "one hundred twenty-eight million, forty-two thousand, nine hundred ninety-one".