1311561321565 has 12 divisors (see below), whose sum is σ = 1729960223292. Its totient is φ = 953862778880.

The previous prime is 1311561321563. The next prime is 1311561321583. The reversal of 1311561321565 is 5651231651131.

It can be written as a sum of positive squares in 2 ways, for example, as 319204660324 + 992356661241 = 564982^2 + 996171^2 .

It is not a de Polignac number, because 1311561321565 - 2¹ = 1311561321563 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1311561321563) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1083934372 + ... + 1083935581.

It is an arithmetic number, because the mean of its divisors is an integer number (144163351941).

Almost surely, 2^{1311561321565} is an apocalyptic number.

It is an amenable number.

1311561321565 is a deficient number, since it is larger than the sum of its proper divisors (418398901727).

1311561321565 is a wasteful number, since it uses less digits than its factorization.

1311561321565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2167869980 (or 2167869969 counting only the distinct ones).

The product of its digits is 81000, while the sum is 40.

Adding to 1311561321565 its reverse (5651231651131), we get a palindrome (6962792972696).

The spelling of 1311561321565 in words is "one trillion, three hundred eleven billion, five hundred sixty-one million, three hundred twenty-one thousand, five hundred sixty-five".