81866851 has 8 divisors (see below), whose sum is σ = 89455104. Its totient is φ = 74302920.

The previous prime is 81866789. The next prime is 81866857. The reversal of 81866851 is 15866818.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81866851 - 2⁷ = 81866723 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81866798 and 81866807.

It is not an unprimeable number, because it can be changed into a prime (81866857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1366 + ... + 12868.

It is an arithmetic number, because the mean of its divisors is an integer number (11181888).

Almost surely, 2^81866851 is an apocalyptic number.

81866851 is a deficient number, since it is larger than the sum of its proper divisors (7588253).

81866851 is a wasteful number, since it uses less digits than its factorization.

81866851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12161.

The product of its digits is 92160, while the sum is 43.

The square root of 81866851 is about 9048.0302276241. The cubic root of 81866851 is about 434.2128734773.

The spelling of 81866851 in words is "eighty-one million, eight hundred sixty-six thousand, eight hundred fifty-one".