20728173 has 4 divisors (see below), whose sum is σ = 27637568. Its totient is φ = 13818780.

The previous prime is 20728159. The next prime is 20728199. The reversal of 20728173 is 37182702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20728173 - 2⁶ = 20728109 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20728173.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728133) 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 in 3 ways as a sum of consecutive naturals, for example, 3454693 + ... + 3454698.

It is an arithmetic number, because the mean of its divisors is an integer number (6909392).

Almost surely, 2^20728173 is an apocalyptic number.

It is an amenable number.

20728173 is a deficient number, since it is larger than the sum of its proper divisors (6909395).

20728173 is an equidigital number, since it uses as much as digits as its factorization.

20728173 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6909394.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 20728173 is about 4552.8203346937. The cubic root of 20728173 is about 274.6968472023.

The spelling of 20728173 in words is "twenty million, seven hundred twenty-eight thousand, one hundred seventy-three".