128781 has 12 divisors (see below), whose sum is σ = 191100. Its totient is φ = 83520.

The previous prime is 128767. The next prime is 128813. The reversal of 128781 is 187821.

It can be written as a sum of positive squares in 2 ways, for example, as 44100 + 84681 = 210^2 + 291^2 .

It is not a de Polignac number, because 128781 - 2⁵ = 128749 is a prime.

It is a super-2 number, since 2×128781² = 33169091922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 128781.

It is not an unprimeable number, because it can be changed into a prime (128761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 195 + ... + 543.

It is an arithmetic number, because the mean of its divisors is an integer number (15925).

2¹²⁸⁷⁸¹ is an apocalyptic number.

It is an amenable number.

128781 is a deficient number, since it is larger than the sum of its proper divisors (62319).

128781 is a wasteful number, since it uses less digits than its factorization.

128781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396 (or 393 counting only the distinct ones).

The product of its digits is 896, while the sum is 27.

The square root of 128781 is about 358.8606972071. The cubic root of 128781 is about 50.4991340570.

It can be divided in two parts, 128 and 781, that added together give a palindrome (909).

The spelling of 128781 in words is "one hundred twenty-eight thousand, seven hundred eighty-one".