1666195649 has 2 divisors, whose sum is σ = 1666195650. Its totient is φ = 1666195648.

The previous prime is 1666195639. The next prime is 1666195673. The reversal of 1666195649 is 9465916661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1534680625 + 131515024 = 39175^2 + 11468^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1666195649 is a prime.

It is a super-3 number, since 3×1666195649³ (a number of 29 digits) contains 333 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 1666195649.

It is not a weakly prime, because it can be changed into another prime (1666195639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833097824 + 833097825.

It is an arithmetic number, because the mean of its divisors is an integer number (833097825).

Almost surely, 2^1666195649 is an apocalyptic number.

It is an amenable number.

1666195649 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666195649 is an equidigital number, since it uses as much as digits as its factorization.

1666195649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2099520, while the sum is 53.

The square root of 1666195649 is about 40819.0598740343. The cubic root of 1666195649 is about 1185.5194003344.

The spelling of 1666195649 in words is "one billion, six hundred sixty-six million, one hundred ninety-five thousand, six hundred forty-nine".