18421813 has 2 divisors, whose sum is σ = 18421814. Its totient is φ = 18421812.

The previous prime is 18421801. The next prime is 18421841. The reversal of 18421813 is 31812481.

It is an a-pointer prime, because the next prime (18421841) can be obtained adding 18421813 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11985444 + 6436369 = 3462^2 + 2537^2 .

It is an emirp because it is prime and its reverse (31812481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18421813 - 2²¹ = 16324661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18421853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9210906 + 9210907.

It is an arithmetic number, because the mean of its divisors is an integer number (9210907).

Almost surely, 2^18421813 is an apocalyptic number.

It is an amenable number.

18421813 is a deficient number, since it is larger than the sum of its proper divisors (1).

18421813 is an equidigital number, since it uses as much as digits as its factorization.

18421813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 28.

The square root of 18421813 is about 4292.0639557211. The cubic root of 18421813 is about 264.1055066888.

It can be divided in two parts, 1842 and 1813, that added together give a triangular number (3655 = T₈₅).

The spelling of 18421813 in words is "eighteen million, four hundred twenty-one thousand, eight hundred thirteen".