66166691 has 2 divisors, whose sum is σ = 66166692. Its totient is φ = 66166690.

The previous prime is 66166663. The next prime is 66166729. The reversal of 66166691 is 19666166.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 66166691 - 2⁶ = 66166627 is a prime.

It is not a weakly prime, because it can be changed into another prime (66166621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33083345 + 33083346.

It is an arithmetic number, because the mean of its divisors is an integer number (33083346).

Almost surely, 2^66166691 is an apocalyptic number.

66166691 is a deficient number, since it is larger than the sum of its proper divisors (1).

66166691 is an equidigital number, since it uses as much as digits as its factorization.

66166691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 41.

The square root of 66166691 is about 8134.2910570006. The cubic root of 66166691 is about 404.4639374240.

The spelling of 66166691 in words is "sixty-six million, one hundred sixty-six thousand, six hundred ninety-one".