6640999 has 4 divisors (see below), whose sum is σ = 7031664. Its totient is φ = 6250336.

The previous prime is 6640993. The next prime is 6641021. The reversal of 6640999 is 9990466.

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 6640999 - 2⁵ = 6640967 is a prime.

It is a Duffinian number.

6640999 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6640993) 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, 195307 + ... + 195340.

It is an arithmetic number, because the mean of its divisors is an integer number (1757916).

Almost surely, 2^6640999 is an apocalyptic number.

6640999 is a deficient number, since it is larger than the sum of its proper divisors (390665).

6640999 is a wasteful number, since it uses less digits than its factorization.

6640999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 390664.

The product of its (nonzero) digits is 104976, while the sum is 43.

The square root of 6640999 is about 2577.0135816483. The cubic root of 6640999 is about 187.9653531294.

The spelling of 6640999 in words is "six million, six hundred forty thousand, nine hundred ninety-nine".