129787121 has 4 divisors (see below), whose sum is σ = 131072244. Its totient is φ = 128502000.

The previous prime is 129787117. The next prime is 129787159. The reversal of 129787121 is 121787921.

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 110986225 + 18800896 = 10535^2 + 4336^2 .

It is a cyclic number.

It is not a de Polignac number, because 129787121 - 2² = 129787117 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (129787171) 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, 642410 + ... + 642611.

It is an arithmetic number, because the mean of its divisors is an integer number (32768061).

Almost surely, 2^129787121 is an apocalyptic number.

It is an amenable number.

129787121 is a deficient number, since it is larger than the sum of its proper divisors (1285123).

129787121 is a wasteful number, since it uses less digits than its factorization.

129787121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1285122.

The product of its digits is 14112, while the sum is 38.

The square root of 129787121 is about 11392.4150644190. The cubic root of 129787121 is about 506.3030375566.

The spelling of 129787121 in words is "one hundred twenty-nine million, seven hundred eighty-seven thousand, one hundred twenty-one".