21790728 has 64 divisors (see below), whose sum is σ = 61344000. Its totient is φ = 7166016.

The previous prime is 21790711. The next prime is 21790801. The reversal of 21790728 is 82709712.

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 = 21790692 and 21790701.

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, 16426 + ... + 17702.

It is an arithmetic number, because the mean of its divisors is an integer number (958500).

Almost surely, 2^21790728 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 21790728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30672000).

21790728 is an abundant number, since it is smaller than the sum of its proper divisors (39553272).

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

21790728 is a wasteful number, since it uses less digits than its factorization.

21790728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1371 (or 1361 counting only the distinct ones).

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

The square root of 21790728 is about 4668.0539842637. The cubic root of 21790728 is about 279.3126337072.

The spelling of 21790728 in words is "twenty-one million, seven hundred ninety thousand, seven hundred twenty-eight".