81660238128 has 600 divisors, whose sum is σ = 289491257088. Its totient is φ = 22180169088.

The previous prime is 81660238067. The next prime is 81660238141. The reversal of 81660238128 is 82183206618.

81660238128 is a `hidden beast` number, since 8 + 1 + 6 + 602 + 38 + 1 + 2 + 8 = 666.

It is a super-2 number, since 2×81660238128² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 500982975 + ... + 500983137.

Almost surely, 2^81660238128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81660238128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144745628544).

81660238128 is an abundant number, since it is smaller than the sum of its proper divisors (207831018960).

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

81660238128 is an equidigital number, since it uses as much as digits as its factorization.

81660238128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241 (or 198 counting only the distinct ones).

The product of its (nonzero) digits is 221184, while the sum is 45.

The spelling of 81660238128 in words is "eighty-one billion, six hundred sixty million, two hundred thirty-eight thousand, one hundred twenty-eight".