31220561 has 2 divisors, whose sum is σ = 31220562. Its totient is φ = 31220560.

The previous prime is 31220521. The next prime is 31220573. The reversal of 31220561 is 16502213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23464336 + 7756225 = 4844^2 + 2785^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31220561 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (31220521) 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, 15610280 + 15610281.

It is an arithmetic number, because the mean of its divisors is an integer number (15610281).

Almost surely, 2^31220561 is an apocalyptic number.

It is an amenable number.

31220561 is a deficient number, since it is larger than the sum of its proper divisors (1).

31220561 is an equidigital number, since it uses as much as digits as its factorization.

31220561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 31220561 is about 5587.5362191220. The cubic root of 31220561 is about 314.8813225564.

Adding to 31220561 its reverse (16502213), we get a palindrome (47722774).

The spelling of 31220561 in words is "thirty-one million, two hundred twenty thousand, five hundred sixty-one".