31389581 has 2 divisors, whose sum is σ = 31389582. Its totient is φ = 31389580.

The previous prime is 31389569. The next prime is 31389601. The reversal of 31389581 is 18598313.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28185481 + 3204100 = 5309^2 + 1790^2 .

It is an emirp because it is prime and its reverse (18598313) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31389581 - 2¹⁴ = 31373197 is a prime.

It is a super-2 number, since 2×31389581² = 1970611590711122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31389551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15694790 + 15694791.

It is an arithmetic number, because the mean of its divisors is an integer number (15694791).

Almost surely, 2^31389581 is an apocalyptic number.

It is an amenable number.

31389581 is a deficient number, since it is larger than the sum of its proper divisors (1).

31389581 is an equidigital number, since it uses as much as digits as its factorization.

31389581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 38.

The square root of 31389581 is about 5602.6405381748. The cubic root of 31389581 is about 315.4485287529.

The spelling of 31389581 in words is "thirty-one million, three hundred eighty-nine thousand, five hundred eighty-one".