31728121321 has 8 divisors (see below), whose sum is σ = 35346979080. Its totient is φ = 28277582592.

The previous prime is 31728121301. The next prime is 31728121361. The reversal of 31728121321 is 12312182713.

It can be written as a sum of positive squares in 4 ways, for example, as 5422849600 + 26305271721 = 73640^2 + 162189^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 31728121321 - 2¹⁷ = 31727990249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31728121301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 42079360 + ... + 42080113.

It is an arithmetic number, because the mean of its divisors is an integer number (4418372385).

Almost surely, 2^31728121321 is an apocalyptic number.

It is an amenable number.

31728121321 is a deficient number, since it is larger than the sum of its proper divisors (3618857759).

31728121321 is a wasteful number, since it uses less digits than its factorization.

31728121321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84159515.

The product of its digits is 4032, while the sum is 31.

The spelling of 31728121321 in words is "thirty-one billion, seven hundred twenty-eight million, one hundred twenty-one thousand, three hundred twenty-one".