161972281 has 4 divisors (see below), whose sum is σ = 162008100. Its totient is φ = 161936464.

The previous prime is 161972231. The next prime is 161972297. The reversal of 161972281 is 182279161.

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 275625 + 161696656 = 525^2 + 12716^2 .

It is a cyclic number.

It is not a de Polignac number, because 161972281 - 2¹¹ = 161970233 is a prime.

It is a super-2 number, since 2×161972281² = 52470039624685922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 161972281.

It is not an unprimeable number, because it can be changed into a prime (161972231) 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, 9946 + ... + 20563.

It is an arithmetic number, because the mean of its divisors is an integer number (40502025).

Almost surely, 2^161972281 is an apocalyptic number.

It is an amenable number.

161972281 is a deficient number, since it is larger than the sum of its proper divisors (35819).

161972281 is an equidigital number, since it uses as much as digits as its factorization.

161972281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35818.

The product of its digits is 12096, while the sum is 37.

The square root of 161972281 is about 12726.8331096153. The cubic root of 161972281 is about 545.1050842455.

The spelling of 161972281 in words is "one hundred sixty-one million, nine hundred seventy-two thousand, two hundred eighty-one".