66806640 has 160 divisors (see below), whose sum is σ = 232752960. Its totient is φ = 17611776.

The previous prime is 66806629. The next prime is 66806687. The reversal of 66806640 is 4660866.

66806640 is a `hidden beast` number, since 6 + 6 + 8 + 0 + 6 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 66806595 and 66806604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 339022 + ... + 339218.

It is an arithmetic number, because the mean of its divisors is an integer number (1454706).

Almost surely, 2^66806640 is an apocalyptic number.

66806640 is a gapful number since it is divisible by the number (60) 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 66806640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116376480).

66806640 is an abundant number, since it is smaller than the sum of its proper divisors (165946320).

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

66806640 is a wasteful number, since it uses less digits than its factorization.

66806640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 376 (or 364 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 66806640 is about 8173.5328958780. The cubic root of 66806640 is about 405.7637166891.

The spelling of 66806640 in words is "sixty-six million, eight hundred six thousand, six hundred forty".