3131221 has 2 divisors, whose sum is σ = 3131222. Its totient is φ = 3131220.

The previous prime is 3131209. The next prime is 3131231. The reversal of 3131221 is 1221313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2340900 + 790321 = 1530^2 + 889^2 .

It is a cyclic number.

It is not a de Polignac number, because 3131221 - 2¹⁵ = 3098453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3131231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1565610 + 1565611.

It is an arithmetic number, because the mean of its divisors is an integer number (1565611).

Almost surely, 2^3131221 is an apocalyptic number.

It is an amenable number.

3131221 is a deficient number, since it is larger than the sum of its proper divisors (1).

3131221 is an equidigital number, since it uses as much as digits as its factorization.

3131221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36, while the sum is 13.

The square root of 3131221 is about 1769.5256426512. The cubic root of 3131221 is about 146.2978376150.

Adding to 3131221 its reverse (1221313), we get a palindrome (4352534).

The spelling of 3131221 in words is "three million, one hundred thirty-one thousand, two hundred twenty-one".