22221821 has 4 divisors (see below), whose sum is σ = 22304700. Its totient is φ = 22138944.

The previous prime is 22221817. The next prime is 22221833. The reversal of 22221821 is 12812222.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12812222 = 2 ⋅6406111.

It can be written as a sum of positive squares in 2 ways, for example, as 1473796 + 20748025 = 1214^2 + 4555^2 .

It is a cyclic number.

It is not a de Polignac number, because 22221821 - 2² = 22221817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 22221793 and 22221802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22281821) 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, 41036 + ... + 41573.

It is an arithmetic number, because the mean of its divisors is an integer number (5576175).

Almost surely, 2^22221821 is an apocalyptic number.

It is an amenable number.

22221821 is a deficient number, since it is larger than the sum of its proper divisors (82879).

22221821 is an equidigital number, since it uses as much as digits as its factorization.

22221821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82878.

The product of its digits is 256, while the sum is 20.

The square root of 22221821 is about 4714.0026516751. The cubic root of 22221821 is about 281.1425297374.

The spelling of 22221821 in words is "twenty-two million, two hundred twenty-one thousand, eight hundred twenty-one".