18291821 has 2 divisors, whose sum is σ = 18291822. Its totient is φ = 18291820.

The previous prime is 18291787. The next prime is 18291839. The reversal of 18291821 is 12819281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10530025 + 7761796 = 3245^2 + 2786^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18291821 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18290821) 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, 9145910 + 9145911.

It is an arithmetic number, because the mean of its divisors is an integer number (9145911).

Almost surely, 2^18291821 is an apocalyptic number.

It is an amenable number.

18291821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18291821 is an equidigital number, since it uses as much as digits as its factorization.

18291821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304, while the sum is 32.

The square root of 18291821 is about 4276.8938495128. The cubic root of 18291821 is about 263.4828268654.

The spelling of 18291821 in words is "eighteen million, two hundred ninety-one thousand, eight hundred twenty-one".