66639638747880 has 320 divisors, whose sum is σ = 246717640540800. Its totient is φ = 15998217776640.

The previous prime is 66639638747873. The next prime is 66639638747893. The reversal of 66639638747880 is 8874783693666.

It is a Harshad number since it is a multiple of its sum of digits (81).

It is a self number, because there is not a number n which added to its sum of digits gives 66639638747880.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 5405775 + ... + 12747614.

It is an arithmetic number, because the mean of its divisors is an integer number (770992626690).

Almost surely, 2^{66639638747880} is an apocalyptic number.

66639638747880 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66639638747880 is an abundant number, since it is smaller than the sum of its proper divisors (180078001792920).

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

66639638747880 is a wasteful number, since it uses less digits than its factorization.

66639638747880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18153526 (or 18153513 counting only the distinct ones).

The product of its (nonzero) digits is 10534551552, while the sum is 81.

The spelling of 66639638747880 in words is "sixty-six trillion, six hundred thirty-nine billion, six hundred thirty-eight million, seven hundred forty-seven thousand, eight hundred eighty".