18643939 has 2 divisors, whose sum is σ = 18643940. Its totient is φ = 18643938.

The previous prime is 18643909. The next prime is 18643943. The reversal of 18643939 is 93934681.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18643939 is a prime.

It is a super-2 number, since 2×18643939² = 695192922871442, which contains 22 as substring.

It is equal to p_1189789 and since 18643939 and 1189789 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 18643895 and 18643904.

It is not a weakly prime, because it can be changed into another prime (18643909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9321969 + 9321970.

It is an arithmetic number, because the mean of its divisors is an integer number (9321970).

Almost surely, 2^18643939 is an apocalyptic number.

18643939 is a deficient number, since it is larger than the sum of its proper divisors (1).

18643939 is an equidigital number, since it uses as much as digits as its factorization.

18643939 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 139968, while the sum is 43.

The square root of 18643939 is about 4317.8627815159. The cubic root of 18643939 is about 265.1627764624.

The spelling of 18643939 in words is "eighteen million, six hundred forty-three thousand, nine hundred thirty-nine".