66501155561666 has 24 divisors (see below), whose sum is σ = 122863479486156. Its totient is φ = 26823995520000.

The previous prime is 66501155561653. The next prime is 66501155561669. The reversal of 66501155561666 is 66616555110566.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 63924742137025 + 2576413424641 = 7995295^2 + 1605121^2 .

It is not an unprimeable number, because it can be changed into a prime (66501155561669) 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 in 11 ways as a sum of consecutive naturals, for example, 19958328335 + ... + 19958331666.

Almost surely, 2^{66501155561666} is an apocalyptic number.

66501155561666 is a deficient number, since it is larger than the sum of its proper divisors (56362323924490).

66501155561666 is a wasteful number, since it uses less digits than its factorization.

66501155561666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39916660034 (or 39916660027 counting only the distinct ones).

The product of its (nonzero) digits is 29160000, while the sum is 59.

The spelling of 66501155561666 in words is "sixty-six trillion, five hundred one billion, one hundred fifty-five million, five hundred sixty-one thousand, six hundred sixty-six".