6669991 has 4 divisors (see below), whose sum is σ = 6885184. Its totient is φ = 6454800.

The previous prime is 6669983. The next prime is 6670019. The reversal of 6669991 is 1999666.

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 6669991 - 2³ = 6669983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6669961) 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, 107550 + ... + 107611.

It is an arithmetic number, because the mean of its divisors is an integer number (1721296).

Almost surely, 2^6669991 is an apocalyptic number.

6669991 is a deficient number, since it is larger than the sum of its proper divisors (215193).

6669991 is a wasteful number, since it uses less digits than its factorization.

6669991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215192.

The product of its digits is 157464, while the sum is 46.

The square root of 6669991 is about 2582.6325716214. The cubic root of 6669991 is about 188.2384837522.

The spelling of 6669991 in words is "six million, six hundred sixty-nine thousand, nine hundred ninety-one".