66991693824 has 672 divisors, whose sum is σ = 230753375424. Its totient is φ = 18496880640.

The previous prime is 66991693823. The next prime is 66991693831. The reversal of 66991693824 is 42839619966.

66991693824 is a `hidden beast` number, since 6 + 6 + 99 + 169 + 382 + 4 = 666.

It is a nude number because it is divisible by every one of its digits.

Its product of digits (30233088) is a multiple of the sum of its prime factors (216).

It is not an unprimeable number, because it can be changed into a prime (66991693823) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 592846792 + ... + 592846904.

Almost surely, 2^66991693824 is an apocalyptic number.

66991693824 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 66991693824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115376687712).

66991693824 is an abundant number, since it is smaller than the sum of its proper divisors (163761681600).

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

66991693824 is a wasteful number, since it uses less digits than its factorization.

66991693824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216 (or 189 counting only the distinct ones).

The product of its digits is 30233088, while the sum is 63.

The spelling of 66991693824 in words is "sixty-six billion, nine hundred ninety-one million, six hundred ninety-three thousand, eight hundred twenty-four".