1661560691057 has 2 divisors, whose sum is σ = 1661560691058. Its totient is φ = 1661560691056.

The previous prime is 1661560690987. The next prime is 1661560691083. The reversal of 1661560691057 is 7501960651661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1163800809616 + 497759881441 = 1078796^2 + 705521^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661560691057 is a prime.

It is not a weakly prime, because it can be changed into another prime (1661560696057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830780345528 + 830780345529.

It is an arithmetic number, because the mean of its divisors is an integer number (830780345529).

Almost surely, 2^{1661560691057} is an apocalyptic number.

It is an amenable number.

1661560691057 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661560691057 is an equidigital number, since it uses as much as digits as its factorization.

1661560691057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2041200, while the sum is 53.

The spelling of 1661560691057 in words is "one trillion, six hundred sixty-one billion, five hundred sixty million, six hundred ninety-one thousand, fifty-seven".