18943987 has 4 divisors (see below), whose sum is σ = 18956376. Its totient is φ = 18931600.

The previous prime is 18943957. The next prime is 18943993. The reversal of 18943987 is 78934981.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 78934981 = 2801 ⋅28181.

It is a cyclic number.

It is not a de Polignac number, because 18943987 - 2¹¹ = 18941939 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18943987.

It is not an unprimeable number, because it can be changed into a prime (18943907) 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 3 ways as a sum of consecutive naturals, for example, 3514 + ... + 7087.

It is an arithmetic number, because the mean of its divisors is an integer number (4739094).

Almost surely, 2^18943987 is an apocalyptic number.

18943987 is a deficient number, since it is larger than the sum of its proper divisors (12389).

18943987 is a wasteful number, since it uses less digits than its factorization.

18943987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12388.

The product of its digits is 435456, while the sum is 49.

The square root of 18943987 is about 4352.4690693904. The cubic root of 18943987 is about 266.5776871535.

The spelling of 18943987 in words is "eighteen million, nine hundred forty-three thousand, nine hundred eighty-seven".