81715643 has 4 divisors (see below), whose sum is σ = 82006728. Its totient is φ = 81424560.

The previous prime is 81715639. The next prime is 81715691. The reversal of 81715643 is 34651718.

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 81715643 - 2² = 81715639 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81715603) 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, 145121 + ... + 145682.

It is an arithmetic number, because the mean of its divisors is an integer number (20501682).

Almost surely, 2^81715643 is an apocalyptic number.

81715643 is a deficient number, since it is larger than the sum of its proper divisors (291085).

81715643 is a wasteful number, since it uses less digits than its factorization.

81715643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291084.

The product of its digits is 20160, while the sum is 35.

The square root of 81715643 is about 9039.6705139070. The cubic root of 81715643 is about 433.9453784600.

The spelling of 81715643 in words is "eighty-one million, seven hundred fifteen thousand, six hundred forty-three".