21070728 has 96 divisors (see below), whose sum is σ = 66044160. Its totient is φ = 5944320.

The previous prime is 21070727. The next prime is 21070739. The reversal of 21070728 is 82707012.

It is not an unprimeable number, because it can be changed into a prime (21070727) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48673 + ... + 49103.

It is an arithmetic number, because the mean of its divisors is an integer number (687960).

Almost surely, 2^21070728 is an apocalyptic number.

21070728 is a gapful number since it is divisible by the number (28) 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 21070728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33022080).

21070728 is an abundant number, since it is smaller than the sum of its proper divisors (44973432).

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

21070728 is a wasteful number, since it uses less digits than its factorization.

21070728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 547 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 1568, while the sum is 27.

The square root of 21070728 is about 4590.2862655830. The cubic root of 21070728 is about 276.2018057788.

The spelling of 21070728 in words is "twenty-one million, seventy thousand, seven hundred twenty-eight".