128643581 has 4 divisors (see below), whose sum is σ = 140338464. Its totient is φ = 116948700.

The previous prime is 128643569. The next prime is 128643611. The reversal of 128643581 is 185346821.

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.

It is not a de Polignac number, because 128643581 - 2²⁶ = 61534717 is a prime.

It is a super-2 number, since 2×128643581² = 33098341865007122, 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 (128642581) 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, 5847425 + ... + 5847446.

It is an arithmetic number, because the mean of its divisors is an integer number (35084616).

Almost surely, 2^128643581 is an apocalyptic number.

128643581 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

128643581 is a deficient number, since it is larger than the sum of its proper divisors (11694883).

128643581 is a wasteful number, since it uses less digits than its factorization.

128643581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11694882.

The product of its digits is 46080, while the sum is 38.

The square root of 128643581 is about 11342.1153670733. The cubic root of 128643581 is about 504.8116554116.

The spelling of 128643581 in words is "one hundred twenty-eight million, six hundred forty-three thousand, five hundred eighty-one".