81728747 has 8 divisors (see below), whose sum is σ = 87489600. Its totient is φ = 76113864.

The previous prime is 81728701. The next prime is 81728771. The reversal of 81728747 is 74782718.

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 81728747 - 2¹⁸ = 81466603 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81728698 and 81728707.

It is not an unprimeable number, because it can be changed into a prime (81728147) 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, 35333 + ... + 37574.

It is an arithmetic number, because the mean of its divisors is an integer number (10936200).

Almost surely, 2^81728747 is an apocalyptic number.

81728747 is a deficient number, since it is larger than the sum of its proper divisors (5760853).

81728747 is a wasteful number, since it uses less digits than its factorization.

81728747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72985.

The product of its digits is 175616, while the sum is 44.

The square root of 81728747 is about 9040.3952900302. The cubic root of 81728747 is about 433.9685731879.

The spelling of 81728747 in words is "eighty-one million, seven hundred twenty-eight thousand, seven hundred forty-seven".