18723213 has 6 divisors (see below), whose sum is σ = 27044654. Its totient is φ = 12482136.

The previous prime is 18723209. The next prime is 18723251. The reversal of 18723213 is 31232781.

It can be written as a sum of positive squares in only one way, i.e., 12236004 + 6487209 = 3498^2 + 2547^2 .

It is not a de Polignac number, because 18723213 - 2² = 18723209 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 (18723203) 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 5 ways as a sum of consecutive naturals, for example, 1040170 + ... + 1040187.

Almost surely, 2^18723213 is an apocalyptic number.

It is an amenable number.

18723213 is a deficient number, since it is larger than the sum of its proper divisors (8321441).

18723213 is a wasteful number, since it uses less digits than its factorization.

18723213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2080363 (or 2080360 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 18723213 is about 4327.0328170699. The cubic root of 18723213 is about 265.5380689557.

Adding to 18723213 its reverse (31232781), we get a palindrome (49955994).

The spelling of 18723213 in words is "eighteen million, seven hundred twenty-three thousand, two hundred thirteen".