81660249 has 24 divisors (see below), whose sum is σ = 128960832. Its totient is φ = 49381920.

The previous prime is 81660223. The next prime is 81660263. The reversal of 81660249 is 94206618.

81660249 is a `hidden beast` number, since 8 + 1 + 6 + 602 + 49 = 666.

It is not a de Polignac number, because 81660249 - 2¹¹ = 81658201 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81660289) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 83964 + ... + 84930.

It is an arithmetic number, because the mean of its divisors is an integer number (5373368).

Almost surely, 2^81660249 is an apocalyptic number.

It is an amenable number.

81660249 is a deficient number, since it is larger than the sum of its proper divisors (47300583).

81660249 is a wasteful number, since it uses less digits than its factorization.

81660249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1837 (or 1834 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 81660249 is about 9036.6060553728. The cubic root of 81660249 is about 433.8473009351.

The spelling of 81660249 in words is "eighty-one million, six hundred sixty thousand, two hundred forty-nine".