31221220221 has 6 divisors (see below), whose sum is σ = 45097318110. Its totient is φ = 20814146808.

The previous prime is 31221220181. The next prime is 31221220237. The reversal of 31221220221 is 12202212213.

31221220221 is a `hidden beast` number, since 3 + 1 + 221 + 220 + 221 = 666.

It can be written as a sum of positive squares in only one way, i.e., 22383152100 + 8838068121 = 149610^2 + 94011^2 .

It is not a de Polignac number, because 31221220221 - 2¹⁸ = 31220958077 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31221220194 and 31221220203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31221220241) 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 5 ways as a sum of consecutive naturals, for example, 1734512226 + ... + 1734512243.

It is an arithmetic number, because the mean of its divisors is an integer number (7516219685).

Almost surely, 2^31221220221 is an apocalyptic number.

It is an amenable number.

31221220221 is a deficient number, since it is larger than the sum of its proper divisors (13876097889).

31221220221 is a wasteful number, since it uses less digits than its factorization.

31221220221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3469024475 (or 3469024472 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

Adding to 31221220221 its reverse (12202212213), we get a palindrome (43423432434).

The spelling of 31221220221 in words is "thirty-one billion, two hundred twenty-one million, two hundred twenty thousand, two hundred twenty-one".