6647999 has 4 divisors (see below), whose sum is σ = 6668064. Its totient is φ = 6627936.

The previous prime is 6647987. The next prime is 6648001. The reversal of 6647999 is 9997466.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9997466 = 2 ⋅4998733.

It is a cyclic number.

It is not a de Polignac number, because 6647999 - 2⁴ = 6647983 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6647909) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9527 + ... + 10200.

It is an arithmetic number, because the mean of its divisors is an integer number (1667016).

Almost surely, 2^6647999 is an apocalyptic number.

6647999 is a deficient number, since it is larger than the sum of its proper divisors (20065).

6647999 is a wasteful number, since it uses less digits than its factorization.

6647999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20064.

The product of its digits is 734832, while the sum is 50.

The square root of 6647999 is about 2578.3713851965. The cubic root of 6647999 is about 188.0313720846.

The spelling of 6647999 in words is "six million, six hundred forty-seven thousand, nine hundred ninety-nine".