161220205 has 4 divisors (see below), whose sum is σ = 193464252. Its totient is φ = 128976160.

The previous prime is 161220161. The next prime is 161220209. The reversal of 161220205 is 502022161.

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 124411716 + 36808489 = 11154^2 + 6067^2 .

It is not a de Polignac number, because 161220205 - 2¹⁷ = 161089133 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161220209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16122016 + ... + 16122025.

It is an arithmetic number, because the mean of its divisors is an integer number (48366063).

Almost surely, 2^161220205 is an apocalyptic number.

It is an amenable number.

161220205 is a deficient number, since it is larger than the sum of its proper divisors (32244047).

161220205 is an equidigital number, since it uses as much as digits as its factorization.

161220205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32244046.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 161220205 is about 12697.2518680225. The cubic root of 161220205 is about 544.2600906753.

Adding to 161220205 its reverse (502022161), we get a palindrome (663242366).

It can be divided in two parts, 16 and 1220205, that added together give a palindrome (1220221).

The spelling of 161220205 in words is "one hundred sixty-one million, two hundred twenty thousand, two hundred five".