18865813 has 2 divisors, whose sum is σ = 18865814. Its totient is φ = 18865812.

The previous prime is 18865799. The next prime is 18865831. The reversal of 18865813 is 31856881.

Together with next prime (18865831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18722929 + 142884 = 4327^2 + 378^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18865813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18865843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9432906 + 9432907.

It is an arithmetic number, because the mean of its divisors is an integer number (9432907).

Almost surely, 2^18865813 is an apocalyptic number.

It is an amenable number.

18865813 is a deficient number, since it is larger than the sum of its proper divisors (1).

18865813 is an equidigital number, since it uses as much as digits as its factorization.

18865813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46080, while the sum is 40.

The square root of 18865813 is about 4343.4793656699. The cubic root of 18865813 is about 266.2104963175.

The spelling of 18865813 in words is "eighteen million, eight hundred sixty-five thousand, eight hundred thirteen".