66440 has 32 divisors (see below), whose sum is σ = 164160. Its totient is φ = 24000.

The previous prime is 66431. The next prime is 66449. The reversal of 66440 is 4466.

66440 is nontrivially palindromic in base 7.

It is an interprime number because it is at equal distance from previous prime (66431) and next prime (66449).

It is a Smith number, since the sum of its digits (20) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a plaindrome in base 9.

It is a nialpdrome in base 10.

It is a zygodrome in base 9.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 66440.

It is not an unprimeable number, because it can be changed into a prime (66449) 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, 365 + ... + 515.

It is an arithmetic number, because the mean of its divisors is an integer number (5130).

2⁶⁶⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (82080).

66440 is an abundant number, since it is smaller than the sum of its proper divisors (97720).

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

66440 is a wasteful number, since it uses less digits than its factorization.

66440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173 (or 169 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 66440 is about 257.7595779016. The cubic root of 66440 is about 40.5020067085.

It can be divided in two parts, 6 and 6440, that added together give a palindrome (6446).

The spelling of 66440 in words is "sixty-six thousand, four hundred forty".