20728 has 8 divisors (see below), whose sum is σ = 38880. Its totient is φ = 10360.

The previous prime is 20719. The next prime is 20731. The reversal of 20728 is 82702.

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (19) coincides with the sum of the digits of its distinct prime factors.

It is a nialpdrome in base 12.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1288 + ... + 1303.

It is an arithmetic number, because the mean of its divisors is an integer number (4860).

2²⁰⁷²⁸ is an apocalyptic number.

It is an amenable number.

20728 is a deficient number, since it is larger than the sum of its proper divisors (18152).

20728 is a wasteful number, since it uses less digits than its factorization.

20728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2597 (or 2593 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 20728 is about 143.9722195425. The cubic root of 20728 is about 27.4696082982.

It can be divided in two parts, 2072 and 8, that added together give a triangular number (2080 = T₆₄).

The spelling of 20728 in words is "twenty thousand, seven hundred twenty-eight".