22091821 has 4 divisors (see below), whose sum is σ = 22454044. Its totient is φ = 21729600.

The previous prime is 22091819. The next prime is 22091869. The reversal of 22091821 is 12819022.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12819022 = 2 ⋅6409511.

It can be written as a sum of positive squares in 2 ways, for example, as 236196 + 21855625 = 486^2 + 4675^2 .

It is a cyclic number.

It is not a de Polignac number, because 22091821 - 2¹ = 22091819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22091021) 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, 181020 + ... + 181141.

It is an arithmetic number, because the mean of its divisors is an integer number (5613511).

Almost surely, 2^22091821 is an apocalyptic number.

It is an amenable number.

22091821 is a deficient number, since it is larger than the sum of its proper divisors (362223).

22091821 is an equidigital number, since it uses as much as digits as its factorization.

22091821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 362222.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 22091821 is about 4700.1937194120. The cubic root of 22091821 is about 280.5932193347.

The spelling of 22091821 in words is "twenty-two million, ninety-one thousand, eight hundred twenty-one".