31521547861 has 2 divisors, whose sum is σ = 31521547862. Its totient is φ = 31521547860.

The previous prime is 31521547823. The next prime is 31521547901. The reversal of 31521547861 is 16874512513.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23234904900 + 8286642961 = 152430^2 + 91031^2 .

It is an emirp because it is prime and its reverse (16874512513) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31521547861 is a prime.

It is a super-3 number, since 3×31521547861³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31521547961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15760773930 + 15760773931.

It is an arithmetic number, because the mean of its divisors is an integer number (15760773931).

Almost surely, 2^31521547861 is an apocalyptic number.

It is an amenable number.

31521547861 is a deficient number, since it is larger than the sum of its proper divisors (1).

31521547861 is an equidigital number, since it uses as much as digits as its factorization.

31521547861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 201600, while the sum is 43.

The spelling of 31521547861 in words is "thirty-one billion, five hundred twenty-one million, five hundred forty-seven thousand, eight hundred sixty-one".