6661691999 has 2 divisors, whose sum is σ = 6661692000. Its totient is φ = 6661691998.

The previous prime is 6661691987. The next prime is 6661692001. The reversal of 6661691999 is 9991961666.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6661691999 is a prime.

Together with 6661692001, it forms a pair of twin primes.

It is a Chen prime.

6661691999 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6661691929) 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, 3330845999 + 3330846000.

It is an arithmetic number, because the mean of its divisors is an integer number (3330846000).

Almost surely, 2^6661691999 is an apocalyptic number.

6661691999 is a deficient number, since it is larger than the sum of its proper divisors (1).

6661691999 is an equidigital number, since it uses as much as digits as its factorization.

6661691999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8503056, while the sum is 62.

The square root of 6661691999 is about 81619.1889141273. The cubic root of 6661691999 is about 1881.6038071226.

The spelling of 6661691999 in words is "six billion, six hundred sixty-one million, six hundred ninety-one thousand, nine hundred ninety-nine".