128767561 has 4 divisors (see below), whose sum is σ = 138672772. Its totient is φ = 118862352.

The previous prime is 128767549. The next prime is 128767577. The reversal of 128767561 is 165767821.

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 16810000 + 111957561 = 4100^2 + 10581^2 .

It is a cyclic number.

It is not a de Polignac number, because 128767561 - 2⁹ = 128767049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (128767531) 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, 4952586 + ... + 4952611.

It is an arithmetic number, because the mean of its divisors is an integer number (34668193).

Almost surely, 2^128767561 is an apocalyptic number.

It is an amenable number.

128767561 is a deficient number, since it is larger than the sum of its proper divisors (9905211).

128767561 is an equidigital number, since it uses as much as digits as its factorization.

128767561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9905210.

The product of its digits is 141120, while the sum is 43.

The square root of 128767561 is about 11347.5795216425. The cubic root of 128767561 is about 504.9737737581.

The spelling of 128767561 in words is "one hundred twenty-eight million, seven hundred sixty-seven thousand, five hundred sixty-one".