20728317 has 4 divisors (see below), whose sum is σ = 27637760. Its totient is φ = 13818876.

The previous prime is 20728291. The next prime is 20728339. The reversal of 20728317 is 71382702.

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 20728317 - 2⁸ = 20728061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728387) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3454717 + ... + 3454722.

It is an arithmetic number, because the mean of its divisors is an integer number (6909440).

Almost surely, 2^20728317 is an apocalyptic number.

It is an amenable number.

20728317 is a deficient number, since it is larger than the sum of its proper divisors (6909443).

20728317 is an equidigital number, since it uses as much as digits as its factorization.

20728317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6909442.

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

The square root of 20728317 is about 4552.8361490394. The cubic root of 20728317 is about 274.6974833133.

The spelling of 20728317 in words is "twenty million, seven hundred twenty-eight thousand, three hundred seventeen".