20661181 has 4 divisors (see below), whose sum is σ = 20678364. Its totient is φ = 20644000.

The previous prime is 20661143. The next prime is 20661191. The reversal of 20661181 is 18116602.

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 8122500 + 12538681 = 2850^2 + 3541^2 .

It is a cyclic number.

It is not a de Polignac number, because 20661181 - 2⁹ = 20660669 is a prime.

It is a super-2 number, since 2×20661181² = 853768800629522, 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 (20661101) 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, 6640 + ... + 9241.

It is an arithmetic number, because the mean of its divisors is an integer number (5169591).

Almost surely, 2^20661181 is an apocalyptic number.

It is an amenable number.

20661181 is a deficient number, since it is larger than the sum of its proper divisors (17183).

20661181 is a wasteful number, since it uses less digits than its factorization.

20661181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17182.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 20661181 is about 4545.4571827265. The cubic root of 20661181 is about 274.4005941743.

Adding to 20661181 its reverse (18116602), we get a palindrome (38777783).

The spelling of 20661181 in words is "twenty million, six hundred sixty-one thousand, one hundred eighty-one".