20728305 has 80 divisors (see below), whose sum is σ = 41631744. Its totient is φ = 9797760.

The previous prime is 20728291. The next prime is 20728339. The reversal of 20728305 is 50382702.

It is not a de Polignac number, because 20728305 - 2⁴ = 20728289 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

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 in 79 ways as a sum of consecutive naturals, for example, 163152 + ... + 163278.

Almost surely, 2^20728305 is an apocalyptic number.

It is an amenable number.

20728305 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

20728305 is a wasteful number, since it uses less digits than its factorization.

20728305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188 (or 179 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 20728305 is about 4552.8348311794. The cubic root of 20728305 is about 274.6974303041.

The spelling of 20728305 in words is "twenty million, seven hundred twenty-eight thousand, three hundred five".