20018993 has 4 divisors (see below), whose sum is σ = 20889408. Its totient is φ = 19148580.

The previous prime is 20018981. The next prime is 20019023. The reversal of 20018993 is 39981002.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 39981002 = 2 ⋅19990501.

It is a cyclic number.

It is not a de Polignac number, because 20018993 - 2²² = 15824689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20018923) 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, 435173 + ... + 435218.

It is an arithmetic number, because the mean of its divisors is an integer number (5222352).

Almost surely, 2^20018993 is an apocalyptic number.

20018993 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

20018993 is a deficient number, since it is larger than the sum of its proper divisors (870415).

20018993 is an equidigital number, since it uses as much as digits as its factorization.

20018993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 870414.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 20018993 is about 4474.2589330525. The cubic root of 20018993 is about 271.5276593640.

Adding to 20018993 its reverse (39981002), we get a palindrome (59999995).

The spelling of 20018993 in words is "twenty million, eighteen thousand, nine hundred ninety-three".