6640020 has 72 divisors (see below), whose sum is σ = 20706504. Its totient is φ = 1721088.

The previous prime is 6640009. The next prime is 6640021. The reversal of 6640020 is 200466.

6640020 is a `hidden beast` number, since 6 + 640 + 0 + 20 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 3090564 + 3549456 = 1758^2 + 1884^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 6639975 and 6640002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6640021) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6162 + ... + 7158.

Almost surely, 2^6640020 is an apocalyptic number.

6640020 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 6640020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10353252).

6640020 is an abundant number, since it is smaller than the sum of its proper divisors (14066484).

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

6640020 is a wasteful number, since it uses less digits than its factorization.

6640020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1049 (or 1044 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 6640020 is about 2576.8236260947. The cubic root of 6640020 is about 187.9561162096.

Adding to 6640020 its reverse (200466), we get a palindrome (6840486).

The spelling of 6640020 in words is "six million, six hundred forty thousand, twenty".