1661501782169 has 2 divisors, whose sum is σ = 1661501782170. Its totient is φ = 1661501782168.

The previous prime is 1661501782159. The next prime is 1661501782177. The reversal of 1661501782169 is 9612871051661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1657947237769 + 3554544400 = 1287613^2 + 59620^2 .

It is an emirp because it is prime and its reverse (9612871051661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1661501782169 - 2⁴ = 1661501782153 is a prime.

It is a super-2 number, since 2×1661501782169² (a number of 25 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661501782169.

It is not a weakly prime, because it can be changed into another prime (1661501782159) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830750891084 + 830750891085.

It is an arithmetic number, because the mean of its divisors is an integer number (830750891085).

Almost surely, 2^{1661501782169} is an apocalyptic number.

It is an amenable number.

1661501782169 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661501782169 is an equidigital number, since it uses as much as digits as its factorization.

1661501782169 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1088640, while the sum is 53.

The spelling of 1661501782169 in words is "one trillion, six hundred sixty-one billion, five hundred one million, seven hundred eighty-two thousand, one hundred sixty-nine".