81691135 has 8 divisors (see below), whose sum is σ = 99270720. Its totient is φ = 64525344.

The previous prime is 81691133. The next prime is 81691163. The reversal of 81691135 is 53119618.

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 81691135 - 2¹ = 81691133 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81691135.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81691133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 103012 + ... + 103801.

It is an arithmetic number, because the mean of its divisors is an integer number (12408840).

Almost surely, 2^81691135 is an apocalyptic number.

81691135 is a deficient number, since it is larger than the sum of its proper divisors (17579585).

81691135 is a wasteful number, since it uses less digits than its factorization.

81691135 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206897.

The product of its digits is 6480, while the sum is 34.

The square root of 81691135 is about 9038.3148318699. The cubic root of 81691135 is about 433.9019914317.

The spelling of 81691135 in words is "eighty-one million, six hundred ninety-one thousand, one hundred thirty-five".