31820666821 has 4 divisors (see below), whose sum is σ = 31821027712. Its totient is φ = 31820305932.

The previous prime is 31820666791. The next prime is 31820666837. The reversal of 31820666821 is 12866602813.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 31820666821 - 2⁷ = 31820666693 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 (31820666021) 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 3 ways as a sum of consecutive naturals, for example, 49426 + ... + 257068.

It is an arithmetic number, because the mean of its divisors is an integer number (7955256928).

Almost surely, 2^31820666821 is an apocalyptic number.

It is an amenable number.

31820666821 is a deficient number, since it is larger than the sum of its proper divisors (360891).

31820666821 is a wasteful number, since it uses less digits than its factorization.

31820666821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360890.

The product of its (nonzero) digits is 165888, while the sum is 43.

The spelling of 31820666821 in words is "thirty-one billion, eight hundred twenty million, six hundred sixty-six thousand, eight hundred twenty-one".