66581144640 has 784 divisors, whose sum is σ = 255696524928. Its totient is φ = 16446799872.

The previous prime is 66581144627. The next prime is 66581144677. The reversal of 66581144640 is 4644118566.

66581144640 is a `hidden beast` number, since 6 + 6 + 581 + 1 + 4 + 4 + 64 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 408473199 + ... + 408473361.

Almost surely, 2^66581144640 is an apocalyptic number.

66581144640 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 66581144640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (127848262464).

66581144640 is an abundant number, since it is smaller than the sum of its proper divisors (189115380288).

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

66581144640 is a wasteful number, since it uses less digits than its factorization.

66581144640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 318 (or 293 counting only the distinct ones).

The product of its (nonzero) digits is 552960, while the sum is 45.

The spelling of 66581144640 in words is "sixty-six billion, five hundred eighty-one million, one hundred forty-four thousand, six hundred forty".