20728756 has 6 divisors (see below), whose sum is σ = 36275330. Its totient is φ = 10364376.

The previous prime is 20728733. The next prime is 20728759. The reversal of 20728756 is 65782702.

It can be written as a sum of positive squares in only one way, i.e., 17892900 + 2835856 = 4230^2 + 1684^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728759) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2591091 + ... + 2591098.

Almost surely, 2^20728756 is an apocalyptic number.

It is an amenable number.

20728756 is a deficient number, since it is larger than the sum of its proper divisors (15546574).

20728756 is a wasteful number, since it uses less digits than its factorization.

20728756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5182193 (or 5182191 counting only the distinct ones).

The product of its (nonzero) digits is 47040, while the sum is 37.

The square root of 20728756 is about 4552.8843604906. The cubic root of 20728756 is about 274.6994225501.

The spelling of 20728756 in words is "twenty million, seven hundred twenty-eight thousand, seven hundred fifty-six".