31997221 has 2 divisors, whose sum is σ = 31997222. Its totient is φ = 31997220.

The previous prime is 31997201. The next prime is 31997227. The reversal of 31997221 is 12279913.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23668225 + 8328996 = 4865^2 + 2886^2 .

It is a cyclic number.

It is not a de Polignac number, because 31997221 - 2⁷ = 31997093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31997227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15998610 + 15998611.

It is an arithmetic number, because the mean of its divisors is an integer number (15998611).

Almost surely, 2^31997221 is an apocalyptic number.

It is an amenable number.

31997221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31997221 is an equidigital number, since it uses as much as digits as its factorization.

31997221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 34.

The square root of 31997221 is about 5656.6086129411. The cubic root of 31997221 is about 317.4710197369.

The spelling of 31997221 in words is "thirty-one million, nine hundred ninety-seven thousand, two hundred twenty-one".