161978399 has 4 divisors (see below), whose sum is σ = 176703720. Its totient is φ = 147253080.

The previous prime is 161978393. The next prime is 161978429. The reversal of 161978399 is 993879161.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161978399 is a prime.

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 161978399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161978393) 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, 7362644 + ... + 7362665.

It is an arithmetic number, because the mean of its divisors is an integer number (44175930).

Almost surely, 2^161978399 is an apocalyptic number.

161978399 is a deficient number, since it is larger than the sum of its proper divisors (14725321).

161978399 is a wasteful number, since it uses less digits than its factorization.

161978399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14725320.

The product of its digits is 734832, while the sum is 53.

The square root of 161978399 is about 12727.0734656479. The cubic root of 161978399 is about 545.1119473764. Note that the first 3 decimals are identical.

The spelling of 161978399 in words is "one hundred sixty-one million, nine hundred seventy-eight thousand, three hundred ninety-nine".