31728188478821 has 16 divisors (see below), whose sum is σ = 32657276590848. Its totient is φ = 30806502988800.

The previous prime is 31728188478809. The next prime is 31728188478827. The reversal of 31728188478821 is 12887488182713.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31728188478821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31728188478827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 332557301 + ... + 332652693.

It is an arithmetic number, because the mean of its divisors is an integer number (2041079786928).

Almost surely, 2^{31728188478821} is an apocalyptic number.

It is an amenable number.

31728188478821 is a deficient number, since it is larger than the sum of its proper divisors (929088112027).

31728188478821 is a wasteful number, since it uses less digits than its factorization.

31728188478821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134092.

The product of its digits is 77070336, while the sum is 68.

The spelling of 31728188478821 in words is "thirty-one trillion, seven hundred twenty-eight billion, one hundred eighty-eight million, four hundred seventy-eight thousand, eight hundred twenty-one".