128366639 has 4 divisors (see below), whose sum is σ = 129290280. Its totient is φ = 127443000.

The previous prime is 128366627. The next prime is 128366681. The reversal of 128366639 is 936663821.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128366639 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 128366639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128366239) 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, 461612 + ... + 461889.

It is an arithmetic number, because the mean of its divisors is an integer number (32322570).

Almost surely, 2^128366639 is an apocalyptic number.

128366639 is a deficient number, since it is larger than the sum of its proper divisors (923641).

128366639 is an equidigital number, since it uses as much as digits as its factorization.

128366639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 923640.

The product of its digits is 279936, while the sum is 44.

The square root of 128366639 is about 11329.9002202138. The cubic root of 128366639 is about 504.4491447941.

The spelling of 128366639 in words is "one hundred twenty-eight million, three hundred sixty-six thousand, six hundred thirty-nine".