81918641 has 12 divisors (see below), whose sum is σ = 95486400. Its totient is φ = 70073640.

The previous prime is 81918637. The next prime is 81918643. The reversal of 81918641 is 14681918.

It is not a de Polignac number, because 81918641 - 2² = 81918637 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81918595 and 81918604.

It is not an unprimeable number, because it can be changed into a prime (81918643) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27956 + ... + 30746.

It is an arithmetic number, because the mean of its divisors is an integer number (7957200).

Almost surely, 2^81918641 is an apocalyptic number.

It is an amenable number.

81918641 is a deficient number, since it is larger than the sum of its proper divisors (13567759).

81918641 is a wasteful number, since it uses less digits than its factorization.

81918641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3404 (or 3397 counting only the distinct ones).

The product of its digits is 13824, while the sum is 38.

The square root of 81918641 is about 9050.8917240237. The cubic root of 81918641 is about 434.3044170185.

The spelling of 81918641 in words is "eighty-one million, nine hundred eighteen thousand, six hundred forty-one".