129831821 has 12 divisors (see below), whose sum is σ = 153881532. Its totient is φ = 109182528.

The previous prime is 129831817. The next prime is 129831833. The reversal of 129831821 is 128138921.

It can be written as a sum of positive squares in 2 ways, for example, as 89965225 + 39866596 = 9485^2 + 6314^2 .

It is not a de Polignac number, because 129831821 - 2² = 129831817 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129831841) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22400 + ... + 27593.

It is an arithmetic number, because the mean of its divisors is an integer number (12823461).

Almost surely, 2^129831821 is an apocalyptic number.

It is an amenable number.

129831821 is a deficient number, since it is larger than the sum of its proper divisors (24049711).

129831821 is an equidigital number, since it uses as much as digits as its factorization.

129831821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50060 (or 50053 counting only the distinct ones).

The product of its digits is 6912, while the sum is 35.

The square root of 129831821 is about 11394.3767271405. The cubic root of 129831821 is about 506.3611561843.

The spelling of 129831821 in words is "one hundred twenty-nine million, eight hundred thirty-one thousand, eight hundred twenty-one".