81889691 has 8 divisors (see below), whose sum is σ = 88494000. Its totient is φ = 75328992.

The previous prime is 81889681. The next prime is 81889739. The reversal of 81889691 is 19698818.

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 81889691 - 2²⁶ = 14780827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81889681) 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 7 ways as a sum of consecutive naturals, for example, 6941 + ... + 14558.

It is an arithmetic number, because the mean of its divisors is an integer number (11061750).

Almost surely, 2^81889691 is an apocalyptic number.

81889691 is a deficient number, since it is larger than the sum of its proper divisors (6604309).

81889691 is a wasteful number, since it uses less digits than its factorization.

81889691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21805.

The product of its digits is 248832, while the sum is 50.

The square root of 81889691 is about 9049.2922927707. The cubic root of 81889691 is about 434.2532500146.

It can be divided in two parts, 818 and 89691, that added together give a palindrome (90509).

The spelling of 81889691 in words is "eighty-one million, eight hundred eighty-nine thousand, six hundred ninety-one".