1661605661593 has 2 divisors, whose sum is σ = 1661605661594. Its totient is φ = 1661605661592.

The previous prime is 1661605661581. The next prime is 1661605661641. The reversal of 1661605661593 is 3951665061661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1446371833104 + 215233828489 = 1202652^2 + 463933^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661605661593 - 2²¹ = 1661603564441 is a prime.

It is a super-2 number, since 2×1661605661593² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1661605661563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830802830796 + 830802830797.

It is an arithmetic number, because the mean of its divisors is an integer number (830802830797).

Almost surely, 2^{1661605661593} is an apocalyptic number.

It is an amenable number.

1661605661593 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661605661593 is an equidigital number, since it uses as much as digits as its factorization.

1661605661593 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5248800, while the sum is 55.

The spelling of 1661605661593 in words is "one trillion, six hundred sixty-one billion, six hundred five million, six hundred sixty-one thousand, five hundred ninety-three".