21723212 has 48 divisors (see below), whose sum is σ = 47029248. Its totient is φ = 8567040.

The previous prime is 21723211. The next prime is 21723227. The reversal of 21723212 is 21232712.

It is not an unprimeable number, because it can be changed into a prime (21723211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21887 + ... + 22857.

It is an arithmetic number, because the mean of its divisors is an integer number (979776).

Almost surely, 2^21723212 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 21723212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23514624).

21723212 is an abundant number, since it is smaller than the sum of its proper divisors (25306036).

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

21723212 is a wasteful number, since it uses less digits than its factorization.

21723212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1046 (or 1044 counting only the distinct ones).

The product of its digits is 336, while the sum is 20.

The square root of 21723212 is about 4660.8166666369. The cubic root of 21723212 is about 279.0238628459.

Adding to 21723212 its reverse (21232712), we get a palindrome (42955924).

The spelling of 21723212 in words is "twenty-one million, seven hundred twenty-three thousand, two hundred twelve".