1666165549 has 2 divisors, whose sum is σ = 1666165550. Its totient is φ = 1666165548.

The previous prime is 1666165511. The next prime is 1666165577. The reversal of 1666165549 is 9455616661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1571726025 + 94439524 = 39645^2 + 9718^2 .

It is an emirp because it is prime and its reverse (9455616661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1666165549 - 2¹¹ = 1666163501 is a prime.

It is a super-2 number, since 2×1666165549² = 5552215273348942802, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1666165049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 833082774 + 833082775.

It is an arithmetic number, because the mean of its divisors is an integer number (833082775).

Almost surely, 2^1666165549 is an apocalyptic number.

It is an amenable number.

1666165549 is a deficient number, since it is larger than the sum of its proper divisors (1).

1666165549 is an equidigital number, since it uses as much as digits as its factorization.

1666165549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1166400, while the sum is 49.

The square root of 1666165549 is about 40818.6911720599. The cubic root of 1666165549 is about 1185.5122614471.

The spelling of 1666165549 in words is "one billion, six hundred sixty-six million, one hundred sixty-five thousand, five hundred forty-nine".