21722212 has 12 divisors (see below), whose sum is σ = 39666816. Its totient is φ = 10388840.

The previous prime is 21722203. The next prime is 21722213. The reversal of 21722212 is 21222712.

It is a self number, because there is not a number n which added to its sum of digits gives 21722212.

It is not an unprimeable number, because it can be changed into a prime (21722213) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 117964 + ... + 118147.

It is an arithmetic number, because the mean of its divisors is an integer number (3305568).

Almost surely, 2^21722212 is an apocalyptic number.

It is an amenable number.

21722212 is a deficient number, since it is larger than the sum of its proper divisors (17944604).

21722212 is a wasteful number, since it uses less digits than its factorization.

21722212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236138 (or 236136 counting only the distinct ones).

The product of its digits is 224, while the sum is 19.

The square root of 21722212 is about 4660.7093880653. The cubic root of 21722212 is about 279.0195812792.

Adding to 21722212 its reverse (21222712), we get a palindrome (42944924).

Subtracting from 21722212 its reverse (21222712), we obtain a triangular number (499500 = T₉₉₉).

It can be divided in two parts, 21722 and 212, that multiplied together give a palindrome (4605064).

The spelling of 21722212 in words is "twenty-one million, seven hundred twenty-two thousand, two hundred twelve".