1265318816521 has 2 divisors, whose sum is σ = 1265318816522. Its totient is φ = 1265318816520.

The previous prime is 1265318816479. The next prime is 1265318816569. The reversal of 1265318816521 is 1256188135621.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1126442595600 + 138876220921 = 1061340^2 + 372661^2 .

It is a cyclic number.

It is not a de Polignac number, because 1265318816521 - 2³¹ = 1263171332873 is a prime.

It is not a weakly prime, because it can be changed into another prime (1265318816621) 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, 632659408260 + 632659408261.

It is an arithmetic number, because the mean of its divisors is an integer number (632659408261).

Almost surely, 2^{1265318816521} is an apocalyptic number.

It is an amenable number.

1265318816521 is a deficient number, since it is larger than the sum of its proper divisors (1).

1265318816521 is an equidigital number, since it uses as much as digits as its factorization.

1265318816521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 691200, while the sum is 49.

The spelling of 1265318816521 in words is "one trillion, two hundred sixty-five billion, three hundred eighteen million, eight hundred sixteen thousand, five hundred twenty-one".