6440040 has 128 divisors (see below), whose sum is σ = 22032000. Its totient is φ = 1672704.

The previous prime is 6440039. The next prime is 6440041. The reversal of 6440040 is 400446.

It is an interprime number because it is at equal distance from previous prime (6440039) and next prime (6440041).

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 = 6439995 and 6440022.

It is not an unprimeable number, because it can be changed into a prime (6440041) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 72316 + ... + 72404.

It is an arithmetic number, because the mean of its divisors is an integer number (172125).

Almost surely, 2^6440040 is an apocalyptic number.

6440040 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 6440040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11016000).

6440040 is an abundant number, since it is smaller than the sum of its proper divisors (15591960).

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

6440040 is a wasteful number, since it uses less digits than its factorization.

6440040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 6440040 is about 2537.7233891817. The cubic root of 6440040 is about 186.0499345640.

Adding to 6440040 its reverse (400446), we get a palindrome (6840486).

It can be divided in two parts, 64 and 40040, that added together give a palindrome (40104).

The spelling of 6440040 in words is "six million, four hundred forty thousand, forty".