20188681 has 4 divisors (see below), whose sum is σ = 20200212. Its totient is φ = 20177152.

The previous prime is 20188667. The next prime is 20188703. The reversal of 20188681 is 18688102.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1836025 + 18352656 = 1355^2 + 4284^2 .

It is a cyclic number.

It is not a de Polignac number, because 20188681 - 2⁹ = 20188169 is a prime.

It is a super-2 number, since 2×20188681² = 815165681039522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20188631) 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, 2536 + ... + 6841.

It is an arithmetic number, because the mean of its divisors is an integer number (5050053).

Almost surely, 2^20188681 is an apocalyptic number.

It is an amenable number.

20188681 is a deficient number, since it is larger than the sum of its proper divisors (11531).

20188681 is an equidigital number, since it uses as much as digits as its factorization.

20188681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11530.

The product of its (nonzero) digits is 6144, while the sum is 34.

The square root of 20188681 is about 4493.1816121764. The cubic root of 20188681 is about 272.2926897276.

The spelling of 20188681 in words is "twenty million, one hundred eighty-eight thousand, six hundred eighty-one".