66555166661 has 2 divisors, whose sum is σ = 66555166662. Its totient is φ = 66555166660.

The previous prime is 66555166637. The next prime is 66555166669. The reversal of 66555166661 is 16666155566.

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., 65430570436 + 1124596225 = 255794^2 + 33535^2 .

It is a cyclic number.

It is not a de Polignac number, because 66555166661 - 2¹⁸ = 66554904517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66555166669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33277583330 + 33277583331.

It is an arithmetic number, because the mean of its divisors is an integer number (33277583331).

Almost surely, 2^66555166661 is an apocalyptic number.

It is an amenable number.

66555166661 is a deficient number, since it is larger than the sum of its proper divisors (1).

66555166661 is an equidigital number, since it uses as much as digits as its factorization.

66555166661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832000, while the sum is 53.

The spelling of 66555166661 in words is "sixty-six billion, five hundred fifty-five million, one hundred sixty-six thousand, six hundred sixty-one".