6691987 has 2 divisors, whose sum is σ = 6691988. Its totient is φ = 6691986.

The previous prime is 6691981. The next prime is 6692017. The reversal of 6691987 is 7891966.

6691987 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 6691987 - 2⁷ = 6691859 is a prime.

It is a Chen prime.

6691987 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (6691981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3345993 + 3345994.

It is an arithmetic number, because the mean of its divisors is an integer number (3345994).

Almost surely, 2^6691987 is an apocalyptic number.

6691987 is a deficient number, since it is larger than the sum of its proper divisors (1).

6691987 is an equidigital number, since it uses as much as digits as its factorization.

6691987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 46.

The square root of 6691987 is about 2586.8875120500. The cubic root of 6691987 is about 188.4451782122.

Subtracting from 6691987 its product of digits (163296), we obtain a triangular number (6528691 = T₃₆₁₃).

The spelling of 6691987 in words is "six million, six hundred ninety-one thousand, nine hundred eighty-seven".