31871921729 has 4 divisors (see below), whose sum is σ = 31985345220. Its totient is φ = 31758498240.

The previous prime is 31871921701. The next prime is 31871921743. The reversal of 31871921729 is 92712917813.

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 10335772225 + 21536149504 = 101665^2 + 146752^2 .

It is a cyclic number.

It is not a de Polignac number, because 31871921729 - 2²⁴ = 31855144513 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 (31871921749) 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, 56711324 + ... + 56711885.

It is an arithmetic number, because the mean of its divisors is an integer number (7996336305).

Almost surely, 2^31871921729 is an apocalyptic number.

It is an amenable number.

31871921729 is a deficient number, since it is larger than the sum of its proper divisors (113423491).

31871921729 is a wasteful number, since it uses less digits than its factorization.

31871921729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 113423490.

The product of its digits is 381024, while the sum is 50.

The spelling of 31871921729 in words is "thirty-one billion, eight hundred seventy-one million, nine hundred twenty-one thousand, seven hundred twenty-nine".