665615385138 has 64 divisors (see below), whose sum is σ = 1480338892800. Its totient is φ = 197837976000.

The previous prime is 665615385133. The next prime is 665615385161. The reversal of 665615385138 is 831583516566.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (665615385133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 246663 + ... + 1179861.

It is an arithmetic number, because the mean of its divisors is an integer number (23130295200).

Almost surely, 2^665615385138 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665615385138, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (740169446400).

665615385138 is an abundant number, since it is smaller than the sum of its proper divisors (814723507662).

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

665615385138 is a wasteful number, since it uses less digits than its factorization.

665615385138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 933423.

The product of its digits is 15552000, while the sum is 57.

The spelling of 665615385138 in words is "six hundred sixty-five billion, six hundred fifteen million, three hundred eighty-five thousand, one hundred thirty-eight".