21721112 has 24 divisors (see below), whose sum is σ = 47377260. Its totient is φ = 9308880.

The previous prime is 21721081. The next prime is 21721127. The reversal of 21721112 is 21112712.

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 27314 + ... + 28097.

Almost surely, 2^21721112 is an apocalyptic number.

It is an amenable number.

21721112 is an abundant number, since it is smaller than the sum of its proper divisors (25656148).

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

21721112 is a wasteful number, since it uses less digits than its factorization.

21721112 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55431 (or 55420 counting only the distinct ones).

The product of its digits is 56, while the sum is 17.

The square root of 21721112 is about 4660.5913787845. The cubic root of 21721112 is about 279.0148714040.

Adding to 21721112 its reverse (21112712), we get a palindrome (42833824).

Subtracting from 21721112 its reverse (21112712), we obtain a square (608400 = 780²).

The spelling of 21721112 in words is "twenty-one million, seven hundred twenty-one thousand, one hundred twelve".