31491289 has 2 divisors, whose sum is σ = 31491290. Its totient is φ = 31491288.

The previous prime is 31491287. The next prime is 31491307. The reversal of 31491289 is 98219413.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19360000 + 12131289 = 4400^2 + 3483^2 .

It is an emirp because it is prime and its reverse (98219413) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31491289 - 2¹ = 31491287 is a prime.

Together with 31491287, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (31491281) 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, 15745644 + 15745645.

It is an arithmetic number, because the mean of its divisors is an integer number (15745645).

Almost surely, 2^31491289 is an apocalyptic number.

It is an amenable number.

31491289 is a deficient number, since it is larger than the sum of its proper divisors (1).

31491289 is an equidigital number, since it uses as much as digits as its factorization.

31491289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 37.

The square root of 31491289 is about 5611.7099889428. The cubic root of 31491289 is about 315.7888651309.

The spelling of 31491289 in words is "thirty-one million, four hundred ninety-one thousand, two hundred eighty-nine".