128255691 has 4 divisors (see below), whose sum is σ = 171007592. Its totient is φ = 85503792.

The previous prime is 128255689. The next prime is 128255723. The reversal of 128255691 is 196552821.

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

It is not a de Polignac number, because 128255691 - 2¹ = 128255689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (128255591) 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, 21375946 + ... + 21375951.

It is an arithmetic number, because the mean of its divisors is an integer number (42751898).

Almost surely, 2^128255691 is an apocalyptic number.

128255691 is a deficient number, since it is larger than the sum of its proper divisors (42751901).

128255691 is an equidigital number, since it uses as much as digits as its factorization.

128255691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42751900.

The product of its digits is 43200, while the sum is 39.

The square root of 128255691 is about 11325.0029139069. The cubic root of 128255691 is about 504.3037701696.

The spelling of 128255691 in words is "one hundred twenty-eight million, two hundred fifty-five thousand, six hundred ninety-one".