18273821 has 4 divisors (see below), whose sum is σ = 18283932. Its totient is φ = 18263712.

The previous prime is 18273809. The next prime is 18273833. The reversal of 18273821 is 12837281.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12837281 = 661 ⋅19421.

It is an interprime number because it is at equal distance from previous prime (18273809) and next prime (18273833).

It can be written as a sum of positive squares in 2 ways, for example, as 12460900 + 5812921 = 3530^2 + 2411^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18273821 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 (18273841) 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 in 3 ways as a sum of consecutive naturals, for example, 1520 + ... + 6233.

It is an arithmetic number, because the mean of its divisors is an integer number (4570983).

Almost surely, 2^18273821 is an apocalyptic number.

It is an amenable number.

18273821 is a deficient number, since it is larger than the sum of its proper divisors (10111).

18273821 is an equidigital number, since it uses as much as digits as its factorization.

18273821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10110.

The product of its digits is 5376, while the sum is 32.

The square root of 18273821 is about 4274.7890006409. The cubic root of 18273821 is about 263.3963720612.

The spelling of 18273821 in words is "eighteen million, two hundred seventy-three thousand, eight hundred twenty-one".