20640181 has 2 divisors, whose sum is σ = 20640182. Its totient is φ = 20640180.

The previous prime is 20640163. The next prime is 20640233. The reversal of 20640181 is 18104602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12489156 + 8151025 = 3534^2 + 2855^2 .

It is a cyclic number.

It is not a de Polignac number, because 20640181 - 2⁵ = 20640149 is a prime.

It is a super-2 number, since 2×20640181² = 852034143425522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20640121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10320090 + 10320091.

It is an arithmetic number, because the mean of its divisors is an integer number (10320091).

Almost surely, 2^20640181 is an apocalyptic number.

It is an amenable number.

20640181 is a deficient number, since it is larger than the sum of its proper divisors (1).

20640181 is an equidigital number, since it uses as much as digits as its factorization.

20640181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 20640181 is about 4543.1465967983. The cubic root of 20640181 is about 274.3075958460.

Adding to 20640181 its reverse (18104602), we get a palindrome (38744783).

The spelling of 20640181 in words is "twenty million, six hundred forty thousand, one hundred eighty-one".