66809664 has 168 divisors, whose sum is σ = 210068160. Its totient is φ = 20782080.

The previous prime is 66809599. The next prime is 66809671. The reversal of 66809664 is 46690866.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1629484 + ... + 1629524.

Almost surely, 2^66809664 is an apocalyptic number.

66809664 is a gapful number since it is divisible by the number (64) 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 66809664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105034080).

66809664 is an abundant number, since it is smaller than the sum of its proper divisors (143258496).

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

66809664 is a wasteful number, since it uses less digits than its factorization.

66809664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126 (or 69 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 66809664 is about 8173.7178811114. The cubic root of 66809664 is about 405.7698388898.

The spelling of 66809664 in words is "sixty-six million, eight hundred nine thousand, six hundred sixty-four".