66400400 has 60 divisors (see below), whose sum is σ = 174040944. Its totient is φ = 24144000.

The previous prime is 66400349. The next prime is 66400403. The reversal of 66400400 is 400466.

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

It is not an unprimeable number, because it can be changed into a prime (66400403) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3146 + ... + 11945.

Almost surely, 2^66400400 is an apocalyptic number.

It is an amenable number.

66400400 is an abundant number, since it is smaller than the sum of its proper divisors (107640544).

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

66400400 is a wasteful number, since it uses less digits than its factorization.

66400400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15120 (or 15109 counting only the distinct ones).

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

The square root of 66400400 is about 8148.6440589831. The cubic root of 66400400 is about 404.9395835295.

Adding to 66400400 its reverse (400466), we get a palindrome (66800866).

The spelling of 66400400 in words is "sixty-six million, four hundred thousand, four hundred".