1321515280781 has 2 divisors, whose sum is σ = 1321515280782. Its totient is φ = 1321515280780.

The previous prime is 1321515280777. The next prime is 1321515280831. The reversal of 1321515280781 is 1870825151231.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 680474858281 + 641040422500 = 824909^2 + 800650^2 .

It is a cyclic number.

It is not a de Polignac number, because 1321515280781 - 2² = 1321515280777 is a prime.

It is a super-2 number, since 2×1321515280781² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1321515280381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 660757640390 + 660757640391.

It is an arithmetic number, because the mean of its divisors is an integer number (660757640391).

Almost surely, 2^{1321515280781} is an apocalyptic number.

It is an amenable number.

1321515280781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1321515280781 is an equidigital number, since it uses as much as digits as its factorization.

1321515280781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 134400, while the sum is 44.

The spelling of 1321515280781 in words is "one trillion, three hundred twenty-one billion, five hundred fifteen million, two hundred eighty thousand, seven hundred eighty-one".