81966819 has 16 divisors (see below), whose sum is σ = 119376000. Its totient is φ = 49613760.

The previous prime is 81966791. The next prime is 81966827. The reversal of 81966819 is 91866918.

It is not a de Polignac number, because 81966819 - 2⁷ = 81966691 is a prime.

It is a super-2 number, since 2×81966819² = 13437118833957522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81966839) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48639 + ... + 50295.

It is an arithmetic number, because the mean of its divisors is an integer number (7461000).

Almost surely, 2^81966819 is an apocalyptic number.

81966819 is a deficient number, since it is larger than the sum of its proper divisors (37409181).

81966819 is a wasteful number, since it uses less digits than its factorization.

81966819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3170.

The product of its digits is 186624, while the sum is 48.

The square root of 81966819 is about 9053.5528385270. The cubic root of 81966819 is about 434.3895413865.

Subtracting 81966819 from its reverse (91866918), we obtain a palindrome (9900099).

The spelling of 81966819 in words is "eighty-one million, nine hundred sixty-six thousand, eight hundred nineteen".