20505161 has 12 divisors (see below), whose sum is σ = 21945600. Its totient is φ = 19153368.

The previous prime is 20505157. The next prime is 20505169. The reversal of 20505161 is 16150502.

It is not a de Polignac number, because 20505161 - 2² = 20505157 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20505169) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28160 + ... + 28878.

It is an arithmetic number, because the mean of its divisors is an integer number (1828800).

Almost surely, 2^20505161 is an apocalyptic number.

It is an amenable number.

20505161 is a deficient number, since it is larger than the sum of its proper divisors (1440439).

20505161 is an equidigital number, since it uses as much as digits as its factorization.

20505161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 836 (or 817 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 20505161 is about 4528.2624703080. The cubic root of 20505161 is about 273.7081491174.

Adding to 20505161 its reverse (16150502), we get a palindrome (36655663).

The spelling of 20505161 in words is "twenty million, five hundred five thousand, one hundred sixty-one".