22187821 has 2 divisors, whose sum is σ = 22187822. Its totient is φ = 22187820.

The previous prime is 22187773. The next prime is 22187843. The reversal of 22187821 is 12878122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22184100 + 3721 = 4710^2 + 61^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-22187821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (22187881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 11093910 + 11093911.

It is an arithmetic number, because the mean of its divisors is an integer number (11093911).

Almost surely, 2^22187821 is an apocalyptic number.

It is an amenable number.

22187821 is a deficient number, since it is larger than the sum of its proper divisors (1).

22187821 is an equidigital number, since it uses as much as digits as its factorization.

22187821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 31.

The square root of 22187821 is about 4710.3949940530. The cubic root of 22187821 is about 280.9990712684. Note that the first 3 decimals are identical.

The spelling of 22187821 in words is "twenty-two million, one hundred eighty-seven thousand, eight hundred twenty-one".