21736728 has 64 divisors (see below), whose sum is σ = 65032800. Its totient is φ = 6687360.

The previous prime is 21736711. The next prime is 21736753. The reversal of 21736728 is 82763712.

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 = 21736692 and 21736701.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1063 + ... + 6678.

Almost surely, 2^21736728 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 21736728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32516400).

21736728 is an abundant number, since it is smaller than the sum of its proper divisors (43296072).

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

21736728 is a wasteful number, since it uses less digits than its factorization.

21736728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7769 (or 7759 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The square root of 21736728 is about 4662.2664016549. The cubic root of 21736728 is about 279.0817196160.

The spelling of 21736728 in words is "twenty-one million, seven hundred thirty-six thousand, seven hundred twenty-eight".