20691728 has 10 divisors (see below), whose sum is σ = 40090254. Its totient is φ = 10345856.

The previous prime is 20691701. The next prime is 20691733. The reversal of 20691728 is 82719602.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20322064 + 369664 = 4508^2 + 608^2 .

It is an unprimeable number.

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, 646601 + ... + 646632.

Almost surely, 2^20691728 is an apocalyptic number.

It is an amenable number.

20691728 is a deficient number, since it is larger than the sum of its proper divisors (19398526).

20691728 is a wasteful number, since it uses less digits than its factorization.

20691728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1293241 (or 1293235 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 20691728 is about 4548.8161097147. The cubic root of 20691728 is about 274.5357588813.

The spelling of 20691728 in words is "twenty million, six hundred ninety-one thousand, seven hundred twenty-eight".