181981566 has 180 divisors, whose sum is σ = 489448872. Its totient is φ = 50409216.

The previous prime is 181981523. The next prime is 181981571. The reversal of 181981566 is 665189181.

181981566 is a `hidden beast` number, since 1 + 8 + 1 + 9 + 81 + 566 = 666.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 89 ways as a sum of consecutive naturals, for example, 7912231 + ... + 7912253.

Almost surely, 2^181981566 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 181981566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (244724436).

181981566 is an abundant number, since it is smaller than the sum of its proper divisors (307467306).

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

181981566 is a wasteful number, since it uses less digits than its factorization.

181981566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97 (or 58 counting only the distinct ones).

The product of its digits is 103680, while the sum is 45.

The square root of 181981566 is about 13490.0543364362. The cubic root of 181981566 is about 566.6859771197.

The spelling of 181981566 in words is "one hundred eighty-one million, nine hundred eighty-one thousand, five hundred sixty-six".