6666691 has 4 divisors (see below), whose sum is σ = 6709312. Its totient is φ = 6624072.

The previous prime is 6666689. The next prime is 6666719. The reversal of 6666691 is 1966666.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6666691 - 2¹ = 6666689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6666391) 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 in 3 ways as a sum of consecutive naturals, for example, 21075 + ... + 21388.

It is an arithmetic number, because the mean of its divisors is an integer number (1677328).

Almost surely, 2^6666691 is an apocalyptic number.

6666691 is a deficient number, since it is larger than the sum of its proper divisors (42621).

6666691 is a wasteful number, since it uses less digits than its factorization.

6666691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42620.

The product of its digits is 69984, while the sum is 40.

The square root of 6666691 is about 2581.9936095970. The cubic root of 6666691 is about 188.2074347614.

It can be divided in two parts, 66666 and 91, that multiplied together give a palindrome (6066606).

The spelling of 6666691 in words is "six million, six hundred sixty-six thousand, six hundred ninety-one".