20728656 has 80 divisors (see below), whose sum is σ = 64093120. Its totient is φ = 6376320.

The previous prime is 20728637. The next prime is 20728691. The reversal of 20728656 is 65682702.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 20728656.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3771 + ... + 7461.

It is an arithmetic number, because the mean of its divisors is an integer number (801164).

Almost surely, 2^20728656 is an apocalyptic number.

20728656 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20728656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32046560).

20728656 is an abundant number, since it is smaller than the sum of its proper divisors (43364464).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20728656 is a wasteful number, since it uses less digits than its factorization.

20728656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3721 (or 3709 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

The square root of 20728656 is about 4552.8733784282. The cubic root of 20728656 is about 274.6989808129.

The spelling of 20728656 in words is "twenty million, seven hundred twenty-eight thousand, six hundred fifty-six".