66689999 has 2 divisors, whose sum is σ = 66690000. Its totient is φ = 66689998.

The previous prime is 66689969. The next prime is 66690017. The reversal of 66689999 is 99998666.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66689999 is a prime.

It is a Sophie Germain prime.

66689999 is a modest number, since divided by 9999 gives 6668 as remainder.

It is a plaindrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66689939) 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 as a sum of consecutive naturals, namely, 33344999 + 33345000.

It is an arithmetic number, because the mean of its divisors is an integer number (33345000).

Almost surely, 2^66689999 is an apocalyptic number.

66689999 is a deficient number, since it is larger than the sum of its proper divisors (1).

66689999 is an equidigital number, since it uses as much as digits as its factorization.

66689999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11337408, while the sum is 62.

The square root of 66689999 is about 8166.3944920632. The cubic root of 66689999 is about 405.5274315089.

The spelling of 66689999 in words is "sixty-six million, six hundred eighty-nine thousand, nine hundred ninety-nine".