161661611 has 4 divisors (see below), whose sum is σ = 161972424. Its totient is φ = 161350800.

The previous prime is 161661589. The next prime is 161661613. The reversal of 161661611 is 116166161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 116166161 = 41 ⋅2833321.

It is a cyclic number.

It is not a de Polignac number, because 161661611 - 2¹⁴ = 161645227 is a prime.

It is a super-2 number, since 2×161661611² = 52268952942230642, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161661613) by changing a digit.

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, 154625 + ... + 155666.

It is an arithmetic number, because the mean of its divisors is an integer number (40493106).

Almost surely, 2^161661611 is an apocalyptic number.

161661611 is a deficient number, since it is larger than the sum of its proper divisors (310813).

161661611 is an equidigital number, since it uses as much as digits as its factorization.

161661611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310812.

The product of its digits is 1296, while the sum is 29.

The square root of 161661611 is about 12714.6219369669. The cubic root of 161661611 is about 544.7563492990.

The spelling of 161661611 in words is "one hundred sixty-one million, six hundred sixty-one thousand, six hundred eleven".