128391786 has 48 divisors (see below), whose sum is σ = 295937928. Its totient is φ = 40089600.

The previous prime is 128391751. The next prime is 128391799. The reversal of 128391786 is 687193821.

It can be written as a sum of positive squares in 4 ways, for example, as 100100025 + 28291761 = 10005^2 + 5319^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 72876 + ... + 74616.

Almost surely, 2^128391786 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 128391786, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147968964).

128391786 is an abundant number, since it is smaller than the sum of its proper divisors (167546142).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

128391786 is a wasteful number, since it uses less digits than its factorization.

128391786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2007 (or 2004 counting only the distinct ones).

The product of its digits is 145152, while the sum is 45.

The square root of 128391786 is about 11331.0099285103. The cubic root of 128391786 is about 504.4820831403.

It can be divided in two parts, 1283917 and 86, that added together give a triangular number (1284003 = T₁₆₀₂).

The spelling of 128391786 in words is "one hundred twenty-eight million, three hundred ninety-one thousand, seven hundred eighty-six".