18939643 has 2 divisors, whose sum is σ = 18939644. Its totient is φ = 18939642.

The previous prime is 18939629. The next prime is 18939647. The reversal of 18939643 is 34693981.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18939643 - 2⁵ = 18939611 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18939643.

It is not a weakly prime, because it can be changed into another prime (18939647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9469821 + 9469822.

It is an arithmetic number, because the mean of its divisors is an integer number (9469822).

Almost surely, 2^18939643 is an apocalyptic number.

18939643 is a deficient number, since it is larger than the sum of its proper divisors (1).

18939643 is an equidigital number, since it uses as much as digits as its factorization.

18939643 is an evil number, because the sum of its binary digits is even.

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

The square root of 18939643 is about 4351.9700136835. The cubic root of 18939643 is about 266.5573095002.

The spelling of 18939643 in words is "eighteen million, nine hundred thirty-nine thousand, six hundred forty-three".