22222221 has 16 divisors (see below), whose sum is σ = 33965184. Its totient is φ = 12659904.

The previous prime is 22222199. The next prime is 22222223. The reversal of 22222221 is 12222222.

It is not a de Polignac number, because 22222221 - 2⁹ = 22221709 is a prime.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 22222221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22222223) 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, 6415 + ... + 9251.

It is an arithmetic number, because the mean of its divisors is an integer number (2122824).

Almost surely, 2^22222221 is an apocalyptic number.

22222221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

22222221 is a deficient number, since it is larger than the sum of its proper divisors (11742963).

22222221 is a wasteful number, since it uses less digits than its factorization.

22222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3220.

The product of its digits is 128, while the sum is 15.

The square root of 22222221 is about 4714.0450782741. The cubic root of 22222221 is about 281.1442166129.

Adding to 22222221 its reverse (12222222), we get a palindrome (34444443).

Subtracting from 22222221 its reverse (12222222), we obtain a palindrome (9999999).

The spelling of 22222221 in words is "twenty-two million, two hundred twenty-two thousand, two hundred twenty-one".