161567581 has 4 divisors (see below), whose sum is σ = 184648672. Its totient is φ = 138486492.

The previous prime is 161567563. The next prime is 161567599. The reversal of 161567581 is 185765161.

161567581 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.

It is an interprime number because it is at equal distance from previous prime (161567563) and next prime (161567599).

It is a cyclic number.

It is not a de Polignac number, because 161567581 - 2⁷ = 161567453 is a prime.

It is a super-2 number, since 2×161567581² = 52208166460383122, 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 (161567521) 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, 11540535 + ... + 11540548.

It is an arithmetic number, because the mean of its divisors is an integer number (46162168).

Almost surely, 2^161567581 is an apocalyptic number.

It is an amenable number.

161567581 is a deficient number, since it is larger than the sum of its proper divisors (23081091).

161567581 is an equidigital number, since it uses as much as digits as its factorization.

161567581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23081090.

The product of its digits is 50400, while the sum is 40.

The square root of 161567581 is about 12710.9236879151. The cubic root of 161567581 is about 544.6507101726.

It can be divided in two parts, 1615 and 67581, that added together give a palindrome (69196).

The spelling of 161567581 in words is "one hundred sixty-one million, five hundred sixty-seven thousand, five hundred eighty-one".