6666640 has 40 divisors (see below), whose sum is σ = 15624000. Its totient is φ = 2645376.

The previous prime is 6666617. The next prime is 6666679. The reversal of 6666640 is 466666.

It is a tau number, because it is divible by the number of its divisors (40).

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 6666596 and 6666605.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13111 + ... + 13609.

It is an arithmetic number, because the mean of its divisors is an integer number (390600).

Almost surely, 2^6666640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6666640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7812000).

6666640 is an abundant number, since it is smaller than the sum of its proper divisors (8957360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6666640 is a wasteful number, since it uses less digits than its factorization.

6666640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 679 (or 673 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 34.

The square root of 6666640 is about 2581.9837334887. The cubic root of 6666640 is about 188.2069548329.

Adding to 6666640 its product of nonzero digits (31104), we get a square (6697744 = 2588²).

The spelling of 6666640 in words is "six million, six hundred sixty-six thousand, six hundred forty".