6405840 has 240 divisors, whose sum is σ = 25998336. Its totient is φ = 1382400.

The previous prime is 6405829. The next prime is 6405877. The reversal of 6405840 is 485046.

6405840 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (240).

It is a super-2 number, since 2×6405840² = 82069572211200, which contains 22 as substring.

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 156220 + ... + 156260.

Almost surely, 2^6405840 is an apocalyptic number.

6405840 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 6405840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (12999168).

6405840 is an abundant number, since it is smaller than the sum of its proper divisors (19592496).

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

6405840 is a wasteful number, since it uses less digits than its factorization.

6405840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 6405840 is about 2530.9760962917. The cubic root of 6405840 is about 185.7200088403.

The spelling of 6405840 in words is "six million, four hundred five thousand, eight hundred forty".