66521207808 has 660 divisors, whose sum is σ = 231427883700. Its totient is φ = 18317967360.

The previous prime is 66521207771. The next prime is 66521207813. The reversal of 66521207808 is 80870212566.

It can be written as a sum of positive squares in 2 ways, for example, as 43717791744 + 22803416064 = 209088^2 + 151008^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 2293834738 + ... + 2293834766.

Almost surely, 2^66521207808 is an apocalyptic number.

66521207808 is a gapful number since it is divisible by the number (68) 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 66521207808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115713941850).

66521207808 is an abundant number, since it is smaller than the sum of its proper divisors (164906675892).

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

66521207808 is a wasteful number, since it uses less digits than its factorization.

66521207808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116 (or 62 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 66521207808 in words is "sixty-six billion, five hundred twenty-one million, two hundred seven thousand, eight hundred eight".