31521551609 has 2 divisors, whose sum is σ = 31521551610. Its totient is φ = 31521551608.

The previous prime is 31521551603. The next prime is 31521551669. The reversal of 31521551609 is 90615512513.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 30623950009 + 897601600 = 174997^2 + 29960^2 .

It is an emirp because it is prime and its reverse (90615512513) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31521551609 is a prime.

It is not a weakly prime, because it can be changed into another prime (31521551603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15760775804 + 15760775805.

It is an arithmetic number, because the mean of its divisors is an integer number (15760775805).

Almost surely, 2^31521551609 is an apocalyptic number.

It is an amenable number.

31521551609 is a deficient number, since it is larger than the sum of its proper divisors (1).

31521551609 is an equidigital number, since it uses as much as digits as its factorization.

31521551609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40500, while the sum is 38.

The spelling of 31521551609 in words is "thirty-one billion, five hundred twenty-one million, five hundred fifty-one thousand, six hundred nine".