31986221 has 2 divisors, whose sum is σ = 31986222. Its totient is φ = 31986220.

The previous prime is 31986209. The next prime is 31986239. The reversal of 31986221 is 12268913.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31516996 + 469225 = 5614^2 + 685^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31986221 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31986271) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15993110 + 15993111.

It is an arithmetic number, because the mean of its divisors is an integer number (15993111).

Almost surely, 2^31986221 is an apocalyptic number.

It is an amenable number.

31986221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31986221 is an equidigital number, since it uses as much as digits as its factorization.

31986221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5184, while the sum is 32.

The square root of 31986221 is about 5655.6362153165. The cubic root of 31986221 is about 317.4346355201.

The spelling of 31986221 in words is "thirty-one million, nine hundred eighty-six thousand, two hundred twenty-one".