161591281 has 4 divisors (see below), whose sum is σ = 161738100. Its totient is φ = 161444464.

The previous prime is 161591279. The next prime is 161591303. The reversal of 161591281 is 182195161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 182195161 = 19 ⋅9589219.

It can be written as a sum of positive squares in 2 ways, for example, as 12531600 + 149059681 = 3540^2 + 12209^2 .

It is a cyclic number.

It is not a de Polignac number, because 161591281 - 2¹ = 161591279 is a prime.

It is a super-2 number, since 2×161591281² = 52223484190441922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161591231) 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, 71746 + ... + 73963.

It is an arithmetic number, because the mean of its divisors is an integer number (40434525).

Almost surely, 2^161591281 is an apocalyptic number.

It is an amenable number.

161591281 is a deficient number, since it is larger than the sum of its proper divisors (146819).

161591281 is a wasteful number, since it uses less digits than its factorization.

161591281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146818.

The product of its digits is 4320, while the sum is 34.

The square root of 161591281 is about 12711.8559227203. The cubic root of 161591281 is about 544.6773400833.

The spelling of 161591281 in words is "one hundred sixty-one million, five hundred ninety-one thousand, two hundred eighty-one".