31666321 has 2 divisors, whose sum is σ = 31666322. Its totient is φ = 31666320.

The previous prime is 31666319. The next prime is 31666343. The reversal of 31666321 is 12366613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28206721 + 3459600 = 5311^2 + 1860^2 .

It is a cyclic number.

It is not a de Polignac number, because 31666321 - 2¹ = 31666319 is a prime.

Together with 31666319, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 31666321.

It is not a weakly prime, because it can be changed into another prime (31666351) 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, 15833160 + 15833161.

It is an arithmetic number, because the mean of its divisors is an integer number (15833161).

Almost surely, 2^31666321 is an apocalyptic number.

It is an amenable number.

31666321 is a deficient number, since it is larger than the sum of its proper divisors (1).

31666321 is an equidigital number, since it uses as much as digits as its factorization.

31666321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 28.

The square root of 31666321 is about 5627.2836253383. The cubic root of 31666321 is about 316.3728474395.

The spelling of 31666321 in words is "thirty-one million, six hundred sixty-six thousand, three hundred twenty-one".