129855818921 has 4 divisors (see below), whose sum is σ = 129867292500. Its totient is φ = 129844345344.

The previous prime is 129855818903. The next prime is 129855818927. The reversal of 129855818921 is 129818558921.

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 32882744896 + 96973074025 = 181336^2 + 311405^2 .

It is a cyclic number.

It is not a de Polignac number, because 129855818921 - 2⁶ = 129855818857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129855818927) 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, 5719796 + ... + 5742453.

It is an arithmetic number, because the mean of its divisors is an integer number (32466823125).

Almost surely, 2^129855818921 is an apocalyptic number.

It is an amenable number.

129855818921 is a deficient number, since it is larger than the sum of its proper divisors (11473579).

129855818921 is a wasteful number, since it uses less digits than its factorization.

129855818921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11473578.

The product of its digits is 4147200, while the sum is 59.

The spelling of 129855818921 in words is "one hundred twenty-nine billion, eight hundred fifty-five million, eight hundred eighteen thousand, nine hundred twenty-one".