31638709 has 2 divisors, whose sum is σ = 31638710. Its totient is φ = 31638708.

The previous prime is 31638707. The next prime is 31638779. The reversal of 31638709 is 90783613.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 29322225 + 2316484 = 5415^2 + 1522^2 .

It is an emirp because it is prime and its reverse (90783613) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31638709 - 2¹ = 31638707 is a prime.

Together with 31638707, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31638707) 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, 15819354 + 15819355.

It is an arithmetic number, because the mean of its divisors is an integer number (15819355).

Almost surely, 2^31638709 is an apocalyptic number.

It is an amenable number.

31638709 is a deficient number, since it is larger than the sum of its proper divisors (1).

31638709 is an equidigital number, since it uses as much as digits as its factorization.

31638709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27216, while the sum is 37.

The square root of 31638709 is about 5624.8296863105. The cubic root of 31638709 is about 316.2808650946.

The spelling of 31638709 in words is "thirty-one million, six hundred thirty-eight thousand, seven hundred nine".