66400 has 36 divisors (see below), whose sum is σ = 164052. Its totient is φ = 26240.

The previous prime is 66383. The next prime is 66403. The reversal of 66400 is 466.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a nialpdrome in base 5 and base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66403) by changing a digit.

66400 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 5 ways as a sum of consecutive naturals, for example, 759 + ... + 841.

It is an arithmetic number, because the mean of its divisors is an integer number (4557).

2⁶⁶⁴⁰⁰ 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 66400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (82026).

66400 is an abundant number, since it is smaller than the sum of its proper divisors (97652).

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

66400 is a wasteful number, since it uses less digits than its factorization.

66400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103 (or 90 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 66400 is about 257.6819745345. The cubic root of 66400 is about 40.4938770401.

Adding to 66400 its reverse (466), we get a palindrome (66866).

The spelling of 66400 in words is "sixty-six thousand, four hundred".