161727981 has 16 divisors (see below), whose sum is σ = 227274240. Its totient is φ = 102014640.

The previous prime is 161727971. The next prime is 161727997. The reversal of 161727981 is 189727161.

It is not a de Polignac number, because 161727981 - 2¹⁷ = 161596909 is a prime.

It is a super-2 number, since 2×161727981² = 52311879676672722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161727901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 65536 + ... + 67958.

It is an arithmetic number, because the mean of its divisors is an integer number (14204640).

Almost surely, 2^161727981 is an apocalyptic number.

It is an amenable number.

161727981 is a deficient number, since it is larger than the sum of its proper divisors (65546259).

161727981 is a wasteful number, since it uses less digits than its factorization.

161727981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3616.

The product of its digits is 42336, while the sum is 42.

The square root of 161727981 is about 12717.2316563000. The cubic root of 161727981 is about 544.8308888097.

The spelling of 161727981 in words is "one hundred sixty-one million, seven hundred twenty-seven thousand, nine hundred eighty-one".