129771561 has 4 divisors (see below), whose sum is σ = 173028752. Its totient is φ = 86514372.

The previous prime is 129771533. The next prime is 129771569. The reversal of 129771561 is 165177921.

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 129771561 - 2¹¹ = 129769513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129771569) 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, 21628591 + ... + 21628596.

It is an arithmetic number, because the mean of its divisors is an integer number (43257188).

Almost surely, 2^129771561 is an apocalyptic number.

It is an amenable number.

129771561 is a deficient number, since it is larger than the sum of its proper divisors (43257191).

129771561 is an equidigital number, since it uses as much as digits as its factorization.

129771561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43257190.

The product of its digits is 26460, while the sum is 39.

The square root of 129771561 is about 11391.7321334378. The cubic root of 129771561 is about 506.2828034223.

The spelling of 129771561 in words is "one hundred twenty-nine million, seven hundred seventy-one thousand, five hundred sixty-one".