161537281 has 4 divisors (see below), whose sum is σ = 171039492. Its totient is φ = 152035072.

The previous prime is 161537273. The next prime is 161537291. The reversal of 161537281 is 182735161.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 138650625 + 22886656 = 11775^2 + 4784^2 .

It is a cyclic number.

It is not a de Polignac number, because 161537281 - 2³ = 161537273 is a prime.

It is a super-2 number, since 2×161537281² = 52188586305745922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161537231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4751080 + ... + 4751113.

It is an arithmetic number, because the mean of its divisors is an integer number (42759873).

Almost surely, 2^161537281 is an apocalyptic number.

It is an amenable number.

161537281 is a deficient number, since it is larger than the sum of its proper divisors (9502211).

161537281 is an equidigital number, since it uses as much as digits as its factorization.

161537281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9502210.

The product of its digits is 10080, while the sum is 34.

The square root of 161537281 is about 12709.7317438253. The cubic root of 161537281 is about 544.6166605443.

The spelling of 161537281 in words is "one hundred sixty-one million, five hundred thirty-seven thousand, two hundred eighty-one".