1321351561661 has 2 divisors, whose sum is σ = 1321351561662. Its totient is φ = 1321351561660.

The previous prime is 1321351561609. The next prime is 1321351561697. The reversal of 1321351561661 is 1661651531231.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 743614753561 + 577736808100 = 862331^2 + 760090^2 .

It is a cyclic number.

It is not a de Polignac number, because 1321351561661 - 2⁶ = 1321351561597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1321351561261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 660675780830 + 660675780831.

It is an arithmetic number, because the mean of its divisors is an integer number (660675780831).

Almost surely, 2^{1321351561661} is an apocalyptic number.

It is an amenable number.

1321351561661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1321351561661 is an equidigital number, since it uses as much as digits as its factorization.

1321351561661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 97200, while the sum is 41.

The spelling of 1321351561661 in words is "one trillion, three hundred twenty-one billion, three hundred fifty-one million, five hundred sixty-one thousand, six hundred sixty-one".