161115561 has 28 divisors (see below), whose sum is σ = 249925380. Its totient is φ = 103692960.

The previous prime is 161115547. The next prime is 161115583. The reversal of 161115561 is 165511161.

It can be written as a sum of positive squares in 2 ways, for example, as 116640000 + 44475561 = 10800^2 + 6669^2 .

It is not a de Polignac number, because 161115561 - 2⁷ = 161115433 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161115761) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 17331 + ... + 24951.

Almost surely, 2^161115561 is an apocalyptic number.

It is an amenable number.

161115561 is a deficient number, since it is larger than the sum of its proper divisors (88809819).

161115561 is an frugal number, since it uses more digits than its factorization.

161115561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7668 (or 7653 counting only the distinct ones).

The product of its digits is 900, while the sum is 27.

The square root of 161115561 is about 12693.1304649405. The cubic root of 161115561 is about 544.1423099878.

The spelling of 161115561 in words is "one hundred sixty-one million, one hundred fifteen thousand, five hundred sixty-one".