161567661 has 4 divisors (see below), whose sum is σ = 215423552. Its totient is φ = 107711772.

The previous prime is 161567647. The next prime is 161567683. The reversal of 161567661 is 166765161.

161567661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 166765161 = 3 ⋅55588387.

It is not a de Polignac number, because 161567661 - 2⁷ = 161567533 is a prime.

It is a super-2 number, since 2×161567661² = 52208218162021842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161567611) 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, 26927941 + ... + 26927946.

It is an arithmetic number, because the mean of its divisors is an integer number (53855888).

Almost surely, 2^161567661 is an apocalyptic number.

It is an amenable number.

161567661 is a deficient number, since it is larger than the sum of its proper divisors (53855891).

161567661 is an equidigital number, since it uses as much as digits as its factorization.

161567661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53855890.

The product of its digits is 45360, while the sum is 39.

The square root of 161567661 is about 12710.9268348142. The cubic root of 161567661 is about 544.6508000670.

The spelling of 161567661 in words is "one hundred sixty-one million, five hundred sixty-seven thousand, six hundred sixty-one".