129988561 has 4 divisors (see below), whose sum is σ = 130313124. Its totient is φ = 129664000.

The previous prime is 129988553. The next prime is 129988597. The reversal of 129988561 is 165889921.

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 129049600 + 938961 = 11360^2 + 969^2 .

It is a cyclic number.

It is not a de Polignac number, because 129988561 - 2³ = 129988553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129988531) 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, 161680 + ... + 162481.

It is an arithmetic number, because the mean of its divisors is an integer number (32578281).

Almost surely, 2^129988561 is an apocalyptic number.

It is an amenable number.

129988561 is a deficient number, since it is larger than the sum of its proper divisors (324563).

129988561 is an equidigital number, since it uses as much as digits as its factorization.

129988561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324562.

The product of its digits is 311040, while the sum is 49.

The square root of 129988561 is about 11401.2526066218. The cubic root of 129988561 is about 506.5648431019.

The spelling of 129988561 in words is "one hundred twenty-nine million, nine hundred eighty-eight thousand, five hundred sixty-one".