21621222 has 64 divisors (see below), whose sum is σ = 56125440. Its totient is φ = 6041088.

The previous prime is 21621181. The next prime is 21621233. The reversal of 21621222 is 22212612.

21621222 is a `hidden beast` number, since 21 + 621 + 2 + 22 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21621195 and 21621204.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17158 + ... + 18374.

It is an arithmetic number, because the mean of its divisors is an integer number (876960).

Almost surely, 2^21621222 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21621222, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28062720).

21621222 is an abundant number, since it is smaller than the sum of its proper divisors (34504218).

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

21621222 is a wasteful number, since it uses less digits than its factorization.

21621222 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1282 (or 1276 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 21621222 is about 4649.8625786146. The cubic root of 21621222 is about 278.5865073833.

Adding to 21621222 its reverse (22212612), we get a palindrome (43833834).

The spelling of 21621222 in words is "twenty-one million, six hundred twenty-one thousand, two hundred twenty-two".