161553661 has 4 divisors (see below), whose sum is σ = 162063612. Its totient is φ = 161043712.

The previous prime is 161553659. The next prime is 161553673. The reversal of 161553661 is 166355161.

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 13176900 + 148376761 = 3630^2 + 12181^2 .

It is a cyclic number.

It is not a de Polignac number, because 161553661 - 2¹ = 161553659 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 (161553361) 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, 254500 + ... + 255133.

It is an arithmetic number, because the mean of its divisors is an integer number (40515903).

Almost surely, 2^161553661 is an apocalyptic number.

It is an amenable number.

161553661 is a deficient number, since it is larger than the sum of its proper divisors (509951).

161553661 is an equidigital number, since it uses as much as digits as its factorization.

161553661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 509950.

The product of its digits is 16200, while the sum is 34.

The square root of 161553661 is about 12710.3761155994. The cubic root of 161553661 is about 544.6350680998.

The spelling of 161553661 in words is "one hundred sixty-one million, five hundred fifty-three thousand, six hundred sixty-one".