31820478821 has 4 divisors (see below), whose sum is σ = 31823162700. Its totient is φ = 31817794944.

The previous prime is 31820478769. The next prime is 31820478869. The reversal of 31820478821 is 12887402813.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12887402813 = 367 ⋅35115539.

It can be written as a sum of positive squares in 2 ways, for example, as 6164448196 + 25656030625 = 78514^2 + 160175^2 .

It is a cyclic number.

It is not a de Polignac number, because 31820478821 - 2⁶ = 31820478757 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 (31820478421) 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, 1324076 + ... + 1347893.

It is an arithmetic number, because the mean of its divisors is an integer number (7955790675).

Almost surely, 2^31820478821 is an apocalyptic number.

It is an amenable number.

31820478821 is a deficient number, since it is larger than the sum of its proper divisors (2683879).

31820478821 is a wasteful number, since it uses less digits than its factorization.

31820478821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2683878.

The product of its (nonzero) digits is 172032, while the sum is 44.

The spelling of 31820478821 in words is "thirty-one billion, eight hundred twenty million, four hundred seventy-eight thousand, eight hundred twenty-one".