31221329 has 2 divisors, whose sum is σ = 31221330. Its totient is φ = 31221328.

The previous prime is 31221317. The next prime is 31221343. The reversal of 31221329 is 92312213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25806400 + 5414929 = 5080^2 + 2327^2 .

It is a cyclic number.

It is not a de Polignac number, because 31221329 - 2²⁴ = 14444113 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (31281329) 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, 15610664 + 15610665.

It is an arithmetic number, because the mean of its divisors is an integer number (15610665).

Almost surely, 2^31221329 is an apocalyptic number.

It is an amenable number.

31221329 is a deficient number, since it is larger than the sum of its proper divisors (1).

31221329 is an equidigital number, since it uses as much as digits as its factorization.

31221329 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 23.

The square root of 31221329 is about 5587.6049430861. The cubic root of 31221329 is about 314.8839044753.

The spelling of 31221329 in words is "thirty-one million, two hundred twenty-one thousand, three hundred twenty-nine".