161220505 has 4 divisors (see below), whose sum is σ = 193464612. Its totient is φ = 128976400.

The previous prime is 161220473. The next prime is 161220511. The reversal of 161220505 is 505022161.

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 40857664 + 120362841 = 6392^2 + 10971^2 .

It is not a de Polignac number, because 161220505 - 2⁵ = 161220473 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

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, 16122046 + ... + 16122055.

It is an arithmetic number, because the mean of its divisors is an integer number (48366153).

Almost surely, 2^161220505 is an apocalyptic number.

It is an amenable number.

161220505 is a deficient number, since it is larger than the sum of its proper divisors (32244107).

161220505 is an equidigital number, since it uses as much as digits as its factorization.

161220505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32244106.

The product of its (nonzero) digits is 600, while the sum is 22.

The square root of 161220505 is about 12697.2636815969. The cubic root of 161220505 is about 544.2604282631.

Adding to 161220505 its reverse (505022161), we get a palindrome (666242666).

The spelling of 161220505 in words is "one hundred sixty-one million, two hundred twenty thousand, five hundred five".