1561279821121 has 2 divisors, whose sum is σ = 1561279821122. Its totient is φ = 1561279821120.

The previous prime is 1561279821083. The next prime is 1561279821139. The reversal of 1561279821121 is 1211289721651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1519647907600 + 41631913521 = 1232740^2 + 204039^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561279821121 - 2⁷ = 1561279820993 is a prime.

It is not a weakly prime, because it can be changed into another prime (1561279821181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780639910560 + 780639910561.

It is an arithmetic number, because the mean of its divisors is an integer number (780639910561).

Almost surely, 2^{1561279821121} is an apocalyptic number.

It is an amenable number.

1561279821121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561279821121 is an equidigital number, since it uses as much as digits as its factorization.

1561279821121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 120960, while the sum is 46.

The spelling of 1561279821121 in words is "one trillion, five hundred sixty-one billion, two hundred seventy-nine million, eight hundred twenty-one thousand, one hundred twenty-one".