66691109 has 2 divisors, whose sum is σ = 66691110. Its totient is φ = 66691108.

The previous prime is 66691103. The next prime is 66691111. The reversal of 66691109 is 90119666.

66691109 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 65529025 + 1162084 = 8095^2 + 1078^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66691109 is a prime.

Together with 66691111, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66691103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33345554 + 33345555.

It is an arithmetic number, because the mean of its divisors is an integer number (33345555).

Almost surely, 2^66691109 is an apocalyptic number.

It is an amenable number.

66691109 is a deficient number, since it is larger than the sum of its proper divisors (1).

66691109 is an equidigital number, since it uses as much as digits as its factorization.

66691109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17496, while the sum is 38.

The square root of 66691109 is about 8166.4624532291. The cubic root of 66691109 is about 405.5296813862.

The spelling of 66691109 in words is "sixty-six million, six hundred ninety-one thousand, one hundred nine".