20513161 has 4 divisors (see below), whose sum is σ = 21013524. Its totient is φ = 20012800.

The previous prime is 20513113. The next prime is 20513177. The reversal of 20513161 is 16131502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16131502 = 2 ⋅8065751.

It can be written as a sum of positive squares in 2 ways, for example, as 7868025 + 12645136 = 2805^2 + 3556^2 .

It is a cyclic number.

It is not a de Polignac number, because 20513161 - 2¹³ = 20504969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20513191) 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, 250120 + ... + 250201.

It is an arithmetic number, because the mean of its divisors is an integer number (5253381).

Almost surely, 2^20513161 is an apocalyptic number.

It is an amenable number.

20513161 is a deficient number, since it is larger than the sum of its proper divisors (500363).

20513161 is an equidigital number, since it uses as much as digits as its factorization.

20513161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500362.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 20513161 is about 4529.1457251892. The cubic root of 20513161 is about 273.7437398400.

Adding to 20513161 its reverse (16131502), we get a palindrome (36644663).

It can be divided in two parts, 205 and 13161, that added together give a triangular number (13366 = T₁₆₃).

The spelling of 20513161 in words is "twenty million, five hundred thirteen thousand, one hundred sixty-one".