31281661 has 2 divisors, whose sum is σ = 31281662. Its totient is φ = 31281660.

The previous prime is 31281643. The next prime is 31281671. The reversal of 31281661 is 16618213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29268100 + 2013561 = 5410^2 + 1419^2 .

It is a cyclic number.

It is not a de Polignac number, because 31281661 - 2⁹ = 31281149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31281611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15640830 + 15640831.

It is an arithmetic number, because the mean of its divisors is an integer number (15640831).

Almost surely, 2^31281661 is an apocalyptic number.

It is an amenable number.

31281661 is a deficient number, since it is larger than the sum of its proper divisors (1).

31281661 is an equidigital number, since it uses as much as digits as its factorization.

31281661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 28.

The square root of 31281661 is about 5593.0010727694. The cubic root of 31281661 is about 315.0866008638.

Adding to 31281661 its reverse (16618213), we get a palindrome (47899874).

The spelling of 31281661 in words is "thirty-one million, two hundred eighty-one thousand, six hundred sixty-one".