129723916561 has 4 divisors (see below), whose sum is σ = 129838819300. Its totient is φ = 129609013824.

The previous prime is 129723916559. The next prime is 129723916573. The reversal of 129723916561 is 165619327921.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165619327921 = 419 ⋅395272859.

It can be written as a sum of positive squares in 2 ways, for example, as 71847585936 + 57876330625 = 268044^2 + 240575^2 .

It is a cyclic number.

It is not a de Polignac number, because 129723916561 - 2¹ = 129723916559 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 129723916499 and 129723916508.

It is not an unprimeable number, because it can be changed into a prime (129723916541) 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, 57449676 + ... + 57451933.

It is an arithmetic number, because the mean of its divisors is an integer number (32459704825).

Almost surely, 2^129723916561 is an apocalyptic number.

It is an amenable number.

129723916561 is a deficient number, since it is larger than the sum of its proper divisors (114902739).

129723916561 is a wasteful number, since it uses less digits than its factorization.

129723916561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114902738.

The product of its digits is 1224720, while the sum is 52.

The spelling of 129723916561 in words is "one hundred twenty-nine billion, seven hundred twenty-three million, nine hundred sixteen thousand, five hundred sixty-one".