6664640 has 56 divisors (see below), whose sum is σ = 16184880. Its totient is φ = 2613248.

The previous prime is 6664631. The next prime is 6664643. The reversal of 6664640 is 464666.

It is a happy number.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 6664597 and 6664606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6664643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18704 + ... + 19056.

Almost surely, 2^6664640 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 6664640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8092440).

6664640 is an abundant number, since it is smaller than the sum of its proper divisors (9520240).

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

6664640 is a wasteful number, since it uses less digits than its factorization.

6664640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429 (or 419 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 32.

The square root of 6664640 is about 2581.5964053275. The cubic root of 6664640 is about 188.1881321798.

The spelling of 6664640 in words is "six million, six hundred sixty-four thousand, six hundred forty".