81728 has 14 divisors (see below), whose sum is σ = 162306. Its totient is φ = 40832.

The previous prime is 81727. The next prime is 81737. The reversal of 81728 is 82718.

It can be written as a sum of positive squares in only one way, i.e., 73984 + 7744 = 272^2 + 88^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81697 and 81706.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 575 + ... + 702.

2⁸¹⁷²⁸ is an apocalyptic number.

It is an amenable number.

81728 is a deficient number, since it is larger than the sum of its proper divisors (80578).

81728 is a wasteful number, since it uses less digits than its factorization.

81728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1289 (or 1279 counting only the distinct ones).

The product of its digits is 896, while the sum is 26.

The square root of 81728 is about 285.8810941633. The cubic root of 81728 is about 43.3967251028.

Subtracting 81728 from its reverse (82718), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 8 and 1728, that multiplied together give a cube (13824 = 24³).

The spelling of 81728 in words is "eighty-one thousand, seven hundred twenty-eight".