20018581 has 4 divisors (see below), whose sum is σ = 21838464. Its totient is φ = 18198700.

The previous prime is 20018567. The next prime is 20018587. The reversal of 20018581 is 18581002.

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.

It is a cyclic number.

It is not a de Polignac number, because 20018581 - 2⁹ = 20018069 is a prime.

It is a super-2 number, since 2×20018581² = 801487170507122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20018587) 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, 909925 + ... + 909946.

It is an arithmetic number, because the mean of its divisors is an integer number (5459616).

Almost surely, 2^20018581 is an apocalyptic number.

It is an amenable number.

20018581 is a deficient number, since it is larger than the sum of its proper divisors (1819883).

20018581 is a wasteful number, since it uses less digits than its factorization.

20018581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1819882.

The product of its (nonzero) digits is 640, while the sum is 25.

The square root of 20018581 is about 4474.2128916716. The cubic root of 20018581 is about 271.5257966302.

Adding to 20018581 its reverse (18581002), we get a palindrome (38599583).

It can be divided in two parts, 200 and 18581, that added together give a palindrome (18781).

The spelling of 20018581 in words is "twenty million, eighteen thousand, five hundred eighty-one".