128939381 has 4 divisors (see below), whose sum is σ = 128989164. Its totient is φ = 128889600.

The previous prime is 128939359. The next prime is 128939399. The reversal of 128939381 is 183939821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 183939821 = 13 ⋅14149217.

It can be written as a sum of positive squares in 2 ways, for example, as 27615025 + 101324356 = 5255^2 + 10066^2 .

It is a cyclic number.

It is not a de Polignac number, because 128939381 - 2¹⁰ = 128938357 is a prime.

It is a super-2 number, since 2×128939381² = 33250727945326322, 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 (128939341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20780 + ... + 26261.

It is an arithmetic number, because the mean of its divisors is an integer number (32247291).

Almost surely, 2^128939381 is an apocalyptic number.

It is an amenable number.

128939381 is a deficient number, since it is larger than the sum of its proper divisors (49783).

128939381 is an equidigital number, since it uses as much as digits as its factorization.

128939381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49782.

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

The square root of 128939381 is about 11355.1477753484. The cubic root of 128939381 is about 505.1982765508.

The spelling of 128939381 in words is "one hundred twenty-eight million, nine hundred thirty-nine thousand, three hundred eighty-one".