128642639 has 2 divisors, whose sum is σ = 128642640. Its totient is φ = 128642638.

The previous prime is 128642629. The next prime is 128642651. The reversal of 128642639 is 936246821.

It is a weak prime.

It is an emirp because it is prime and its reverse (936246821) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128642639 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 128642596 and 128642605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128642629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64321319 + 64321320.

It is an arithmetic number, because the mean of its divisors is an integer number (64321320).

Almost surely, 2^128642639 is an apocalyptic number.

128642639 is a deficient number, since it is larger than the sum of its proper divisors (1).

128642639 is an equidigital number, since it uses as much as digits as its factorization.

128642639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 124416, while the sum is 41.

The square root of 128642639 is about 11342.0738403521. The cubic root of 128642639 is about 504.8104232379.

The spelling of 128642639 in words is "one hundred twenty-eight million, six hundred forty-two thousand, six hundred thirty-nine".