6645991 has 8 divisors (see below), whose sum is σ = 7632000. Its totient is φ = 5723640.

The previous prime is 6645983. The next prime is 6646001. The reversal of 6645991 is 1995466.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6645991 - 2³ = 6645983 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 (6645911) 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 7 ways as a sum of consecutive naturals, for example, 15691 + ... + 16108.

It is an arithmetic number, because the mean of its divisors is an integer number (954000).

Almost surely, 2^6645991 is an apocalyptic number.

6645991 is a deficient number, since it is larger than the sum of its proper divisors (986009).

6645991 is a wasteful number, since it uses less digits than its factorization.

6645991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31829.

The product of its digits is 58320, while the sum is 40.

The square root of 6645991 is about 2577.9819626987. The cubic root of 6645991 is about 188.0124388178.

The spelling of 6645991 in words is "six million, six hundred forty-five thousand, nine hundred ninety-one".