128638381 has 4 divisors (see below), whose sum is σ = 132115132. Its totient is φ = 125161632.

The previous prime is 128638357. The next prime is 128638397. The reversal of 128638381 is 183836821.

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

It can be written as a sum of positive squares in 2 ways, for example, as 48177481 + 80460900 = 6941^2 + 8970^2 .

It is a cyclic number.

It is not a de Polignac number, because 128638381 - 2²¹ = 126541229 is a prime.

It is a super-2 number, since 2×128638381² = 33095666132602322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128638981) 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, 1738320 + ... + 1738393.

It is an arithmetic number, because the mean of its divisors is an integer number (33028783).

Almost surely, 2^128638381 is an apocalyptic number.

It is an amenable number.

128638381 is a deficient number, since it is larger than the sum of its proper divisors (3476751).

128638381 is an equidigital number, since it uses as much as digits as its factorization.

128638381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3476750.

The product of its digits is 55296, while the sum is 40.

The square root of 128638381 is about 11341.8861306222. The cubic root of 128638381 is about 504.8048535281.

The spelling of 128638381 in words is "one hundred twenty-eight million, six hundred thirty-eight thousand, three hundred eighty-one".