6638640 has 80 divisors (see below), whose sum is σ = 20832000. Its totient is φ = 1748736.

The previous prime is 6638633. The next prime is 6638647. The reversal of 6638640 is 468366.

It is an interprime number because it is at equal distance from previous prime (6638633) and next prime (6638647).

It is a tau number, because it is divible by the number of its divisors (80).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6638647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 33261 + ... + 33459.

It is an arithmetic number, because the mean of its divisors is an integer number (260400).

Almost surely, 2^6638640 is an apocalyptic number.

6638640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6638640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10416000).

6638640 is an abundant number, since it is smaller than the sum of its proper divisors (14193360).

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

6638640 is a wasteful number, since it uses less digits than its factorization.

6638640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 354 (or 348 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 33.

The square root of 6638640 is about 2576.5558406524. Note that the first 3 decimals coincide. The cubic root of 6638640 is about 187.9430942905.

The spelling of 6638640 in words is "six million, six hundred thirty-eight thousand, six hundred forty".