20508161 has 4 divisors (see below), whose sum is σ = 20580912. Its totient is φ = 20435412.

The previous prime is 20508113. The next prime is 20508167. The reversal of 20508161 is 16180502.

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-20508161 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20508167) 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 3 ways as a sum of consecutive naturals, for example, 35951 + ... + 36516.

It is an arithmetic number, because the mean of its divisors is an integer number (5145228).

Almost surely, 2^20508161 is an apocalyptic number.

It is an amenable number.

20508161 is a deficient number, since it is larger than the sum of its proper divisors (72751).

20508161 is an equidigital number, since it uses as much as digits as its factorization.

20508161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72750.

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 20508161 is about 4528.5937110763. The cubic root of 20508161 is about 273.7214967230.

Adding to 20508161 its reverse (16180502), we get a palindrome (36688663).

The spelling of 20508161 in words is "twenty million, five hundred eight thousand, one hundred sixty-one".