128389391 has 4 divisors (see below), whose sum is σ = 138265512. Its totient is φ = 118513272.

The previous prime is 128389367. The next prime is 128389439. The reversal of 128389391 is 193983821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 193983821 = 17 ⋅11410813.

It is a cyclic number.

It is not a de Polignac number, because 128389391 - 2²² = 124195087 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 (128389091) 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, 4938041 + ... + 4938066.

It is an arithmetic number, because the mean of its divisors is an integer number (34566378).

Almost surely, 2^128389391 is an apocalyptic number.

128389391 is a deficient number, since it is larger than the sum of its proper divisors (9876121).

128389391 is an equidigital number, since it uses as much as digits as its factorization.

128389391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9876120.

The product of its digits is 93312, while the sum is 44.

The square root of 128389391 is about 11330.9042445870. The cubic root of 128389391 is about 504.4789462779.

The spelling of 128389391 in words is "one hundred twenty-eight million, three hundred eighty-nine thousand, three hundred ninety-one".