128236781 has 4 divisors (see below), whose sum is σ = 128600412. Its totient is φ = 127873152.

The previous prime is 128236777. The next prime is 128236789. The reversal of 128236781 is 187632821.

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 78039556 + 50197225 = 8834^2 + 7085^2 .

It is a cyclic number.

It is not a de Polignac number, because 128236781 - 2² = 128236777 is a prime.

It is a super-2 number, since 2×128236781² = 32889344002483922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128236789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 181286 + ... + 181991.

It is an arithmetic number, because the mean of its divisors is an integer number (32150103).

Almost surely, 2^128236781 is an apocalyptic number.

It is an amenable number.

128236781 is a deficient number, since it is larger than the sum of its proper divisors (363631).

128236781 is an equidigital number, since it uses as much as digits as its factorization.

128236781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363630.

The product of its digits is 32256, while the sum is 38.

The square root of 128236781 is about 11324.1680047587. The cubic root of 128236781 is about 504.2789841271.

The spelling of 128236781 in words is "one hundred twenty-eight million, two hundred thirty-six thousand, seven hundred eighty-one".