66556836864 has 616 divisors, whose sum is σ = 233688926208. Its totient is φ = 18542960640.

The previous prime is 66556836839. The next prime is 66556836919. The reversal of 66556836864 is 46863865566.

It is a happy number.

66556836864 is a `hidden beast` number, since 6 + 6 + 5 + 568 + 3 + 6 + 8 + 64 = 666.

66556836864 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×66556836864² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 245597049 + ... + 245597319.

Almost surely, 2^66556836864 is an apocalyptic number.

66556836864 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 66556836864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116844463104).

66556836864 is an abundant number, since it is smaller than the sum of its proper divisors (167132089344).

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

66556836864 is an equidigital number, since it uses as much as digits as its factorization.

66556836864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363 (or 330 counting only the distinct ones).

The product of its digits is 149299200, while the sum is 63.

The spelling of 66556836864 in words is "sixty-six billion, five hundred fifty-six million, eight hundred thirty-six thousand, eight hundred sixty-four".