31313220221 has 4 divisors (see below), whose sum is σ = 31314217152. Its totient is φ = 31312223292.

The previous prime is 31313220217. The next prime is 31313220251. The reversal of 31313220221 is 12202231313.

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.

It is a cyclic number.

It is not a de Polignac number, because 31313220221 - 2² = 31313220217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31313220193 and 31313220202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31313220251) 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, 449765 + ... + 514698.

It is an arithmetic number, because the mean of its divisors is an integer number (7828554288).

Almost surely, 2^31313220221 is an apocalyptic number.

It is an amenable number.

31313220221 is a deficient number, since it is larger than the sum of its proper divisors (996931).

31313220221 is an equidigital number, since it uses as much as digits as its factorization.

31313220221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 996930.

The product of its (nonzero) digits is 432, while the sum is 20.

Adding to 31313220221 its reverse (12202231313), we get a palindrome (43515451534).

The spelling of 31313220221 in words is "thirty-one billion, three hundred thirteen million, two hundred twenty thousand, two hundred twenty-one".