20638181 has 4 divisors (see below), whose sum is σ = 20700864. Its totient is φ = 20575500.

The previous prime is 20638171. The next prime is 20638201. The reversal of 20638181 is 18183602.

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 a de Polignac number, because none of the positive numbers 2^k-20638181 is a prime.

It is a super-2 number, since 2×20638181² = 851869029977522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20638171) 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, 30845 + ... + 31506.

It is an arithmetic number, because the mean of its divisors is an integer number (5175216).

Almost surely, 2^20638181 is an apocalyptic number.

It is an amenable number.

20638181 is a deficient number, since it is larger than the sum of its proper divisors (62683).

20638181 is an equidigital number, since it uses as much as digits as its factorization.

20638181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62682.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 20638181 is about 4542.9264797045. The cubic root of 20638181 is about 274.2987355730.

The spelling of 20638181 in words is "twenty million, six hundred thirty-eight thousand, one hundred eighty-one".