31281389 has 2 divisors, whose sum is σ = 31281390. Its totient is φ = 31281388.

The previous prime is 31281379. The next prime is 31281413. The reversal of 31281389 is 98318213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27510025 + 3771364 = 5245^2 + 1942^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31281389 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31281329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15640694 + 15640695.

It is an arithmetic number, because the mean of its divisors is an integer number (15640695).

Almost surely, 2^31281389 is an apocalyptic number.

It is an amenable number.

31281389 is a deficient number, since it is larger than the sum of its proper divisors (1).

31281389 is an equidigital number, since it uses as much as digits as its factorization.

31281389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 31281389 is about 5592.9767566118. The cubic root of 31281389 is about 315.0856876151.

The spelling of 31281389 in words is "thirty-one million, two hundred eighty-one thousand, three hundred eighty-nine".