81664243 has 8 divisors (see below), whose sum is σ = 86715360. Its totient is φ = 76640640.

The previous prime is 81664241. The next prime is 81664249. The reversal of 81664243 is 34246618.

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 81664243 - 2¹ = 81664241 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81664199 and 81664208.

It is not an unprimeable number, because it can be changed into a prime (81664241) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 588 + ... + 12793.

It is an arithmetic number, because the mean of its divisors is an integer number (10839420).

Almost surely, 2^81664243 is an apocalyptic number.

81664243 is a deficient number, since it is larger than the sum of its proper divisors (5051117).

81664243 is a wasteful number, since it uses less digits than its factorization.

81664243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13757.

The product of its digits is 27648, while the sum is 34.

The square root of 81664243 is about 9036.8270427180. The cubic root of 81664243 is about 433.8543739721.

The spelling of 81664243 in words is "eighty-one million, six hundred sixty-four thousand, two hundred forty-three".