20728815 has 8 divisors (see below), whose sum is σ = 33166128. Its totient is φ = 11055360.

The previous prime is 20728811. The next prime is 20728817. The reversal of 20728815 is 51882702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20728815 - 2² = 20728811 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 690946 + ... + 690975.

It is an arithmetic number, because the mean of its divisors is an integer number (4145766).

Almost surely, 2^20728815 is an apocalyptic number.

20728815 is a deficient number, since it is larger than the sum of its proper divisors (12437313).

20728815 is a wasteful number, since it uses less digits than its factorization.

20728815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1381929.

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 20728815 is about 4552.8908398950. The cubic root of 20728815 is about 274.6996831743.

The spelling of 20728815 in words is "twenty million, seven hundred twenty-eight thousand, eight hundred fifteen".