81646879 has 4 divisors (see below), whose sum is σ = 81811000. Its totient is φ = 81482760.

The previous prime is 81646841. The next prime is 81646883. The reversal of 81646879 is 97864618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81646879 - 2¹⁵ = 81614111 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81646889) 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 3 ways as a sum of consecutive naturals, for example, 81312 + ... + 82309.

It is an arithmetic number, because the mean of its divisors is an integer number (20452750).

Almost surely, 2^81646879 is an apocalyptic number.

81646879 is a deficient number, since it is larger than the sum of its proper divisors (164121).

81646879 is a wasteful number, since it uses less digits than its factorization.

81646879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164120.

The product of its digits is 580608, while the sum is 49.

The square root of 81646879 is about 9035.8662562037. The cubic root of 81646879 is about 433.8236221151.

The spelling of 81646879 in words is "eighty-one million, six hundred forty-six thousand, eight hundred seventy-nine".