128528781 has 4 divisors (see below), whose sum is σ = 171371712. Its totient is φ = 85685852.

The previous prime is 128528779. The next prime is 128528791. The reversal of 128528781 is 187825821.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 187825821 = 3 ⋅62608607.

It is a cyclic number.

It is not a de Polignac number, because 128528781 - 2¹ = 128528779 is a prime.

It is a super-2 number, since 2×128528781² = 33039295090691922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128528791) 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, 21421461 + ... + 21421466.

It is an arithmetic number, because the mean of its divisors is an integer number (42842928).

Almost surely, 2^128528781 is an apocalyptic number.

It is an amenable number.

128528781 is a deficient number, since it is larger than the sum of its proper divisors (42842931).

128528781 is an equidigital number, since it uses as much as digits as its factorization.

128528781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42842930.

The product of its digits is 71680, while the sum is 42.

The square root of 128528781 is about 11337.0534531685. The cubic root of 128528781 is about 504.6614480848.

The spelling of 128528781 in words is "one hundred twenty-eight million, five hundred twenty-eight thousand, seven hundred eighty-one".