20917728 has 144 divisors (see below), whose sum is σ = 66227616. Its totient is φ = 6220800.

The previous prime is 20917717. The next prime is 20917733. The reversal of 20917728 is 82771902.

It is a tau number, because it is divible by the number of its divisors (144).

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

It is a junction number, because it is equal to n+sod(n) for n = 20917692 and 20917701.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 138453 + ... + 138603.

It is an arithmetic number, because the mean of its divisors is an integer number (459914).

Almost surely, 2^20917728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20917728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33113808).

20917728 is an abundant number, since it is smaller than the sum of its proper divisors (45309888).

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

20917728 is a wasteful number, since it uses less digits than its factorization.

20917728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 206 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 20917728 is about 4573.5902746092. The cubic root of 20917728 is about 275.5316568860.

The spelling of 20917728 in words is "twenty million, nine hundred seventeen thousand, seven hundred twenty-eight".