161978369 has 12 divisors (see below), whose sum is σ = 194922900. Its totient is φ = 134049888.

The previous prime is 161978359. The next prime is 161978387. The reversal of 161978369 is 963879161.

It can be written as a sum of positive squares in 2 ways, for example, as 124032769 + 37945600 = 11137^2 + 6160^2 .

It is not a de Polignac number, because 161978369 - 2¹² = 161974273 is a prime.

It is a super-2 number, since 2×161978369² = 52473984047800322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (161978339) 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 11 ways as a sum of consecutive naturals, for example, 55574 + ... + 58415.

It is an arithmetic number, because the mean of its divisors is an integer number (16243575).

Almost surely, 2^161978369 is an apocalyptic number.

It is an amenable number.

161978369 is a deficient number, since it is larger than the sum of its proper divisors (32944531).

161978369 is a wasteful number, since it uses less digits than its factorization.

161978369 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114032 (or 114025 counting only the distinct ones).

The product of its digits is 489888, while the sum is 50.

The square root of 161978369 is about 12727.0722870580. The cubic root of 161978369 is about 545.1119137230. Note that the first 3 decimals are identical.

The spelling of 161978369 in words is "one hundred sixty-one million, nine hundred seventy-eight thousand, three hundred sixty-nine".