20018861 has 4 divisors (see below), whose sum is σ = 20034300. Its totient is φ = 20003424.

The previous prime is 20018849. The next prime is 20018881. The reversal of 20018861 is 16881002.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7873636 + 12145225 = 2806^2 + 3485^2 .

It is a cyclic number.

It is not a de Polignac number, because 20018861 - 2¹⁸ = 19756717 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 20018861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20018821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5576 + ... + 8433.

It is an arithmetic number, because the mean of its divisors is an integer number (5008575).

Almost surely, 2^20018861 is an apocalyptic number.

It is an amenable number.

20018861 is a deficient number, since it is larger than the sum of its proper divisors (15439).

20018861 is a wasteful number, since it uses less digits than its factorization.

20018861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15438.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 20018861 is about 4474.2441819820. The cubic root of 20018861 is about 271.5270625685.

Adding to 20018861 its reverse (16881002), we get a palindrome (36899863).

The spelling of 20018861 in words is "twenty million, eighteen thousand, eight hundred sixty-one".