128999581 has 4 divisors (see below), whose sum is σ = 129865500. Its totient is φ = 128133664.

The previous prime is 128999579. The next prime is 128999597. The reversal of 128999581 is 185999821.

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 7338681 + 121660900 = 2709^2 + 11030^2 .

It is a cyclic number.

It is not a de Polignac number, because 128999581 - 2¹ = 128999579 is a prime.

It is a super-2 number, since 2×128999581² = 33281783796351122, 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 (128999551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 432736 + ... + 433033.

It is an arithmetic number, because the mean of its divisors is an integer number (32466375).

Almost surely, 2^128999581 is an apocalyptic number.

It is an amenable number.

128999581 is a deficient number, since it is larger than the sum of its proper divisors (865919).

128999581 is an equidigital number, since it uses as much as digits as its factorization.

128999581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 865918.

The product of its digits is 466560, while the sum is 52.

The square root of 128999581 is about 11357.7982461391. The cubic root of 128999581 is about 505.2768876628.

The spelling of 128999581 in words is "one hundred twenty-eight million, nine hundred ninety-nine thousand, five hundred eighty-one".