66840 has 32 divisors (see below), whose sum is σ = 200880. Its totient is φ = 17792.

The previous prime is 66821. The next prime is 66841. The reversal of 66840 is 4866.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 66840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 159 + ... + 398.

2⁶⁶⁸⁴⁰ is an apocalyptic number.

66840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66840 is an abundant number, since it is smaller than the sum of its proper divisors (134040).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100440).

66840 is a wasteful number, since it uses less digits than its factorization.

66840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 571 (or 567 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 66840 is about 258.5343304089. The cubic root of 66840 is about 40.5831245032.

The spelling of 66840 in words is "sixty-six thousand, eight hundred forty".