21728070 has 144 divisors (see below), whose sum is σ = 70958160. Its totient is φ = 4572288.

The previous prime is 21728051. The next prime is 21728071. The reversal of 21728070 is 7082712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21728071) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 57141 + ... + 57519.

It is an arithmetic number, because the mean of its divisors is an integer number (492765).

Almost surely, 2^21728070 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21728070, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35479080).

21728070 is an abundant number, since it is smaller than the sum of its proper divisors (49230090).

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

21728070 is a wasteful number, since it uses less digits than its factorization.

21728070 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 419 (or 409 counting only the distinct ones).

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

The square root of 21728070 is about 4661.3377908064. The cubic root of 21728070 is about 279.0446608276.

The spelling of 21728070 in words is "twenty-one million, seven hundred twenty-eight thousand, seventy".