181681399 has 4 divisors (see below), whose sum is σ = 183379464. Its totient is φ = 179983336.

The previous prime is 181681369. The next prime is 181681417. The reversal of 181681399 is 993186181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 993186181 = 13 ⋅76398937.

It is a cyclic number.

It is not a de Polignac number, because 181681399 - 2⁷ = 181681271 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181681369) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 848872 + ... + 849085.

It is an arithmetic number, because the mean of its divisors is an integer number (45844866).

Almost surely, 2^181681399 is an apocalyptic number.

181681399 is a deficient number, since it is larger than the sum of its proper divisors (1698065).

181681399 is a wasteful number, since it uses less digits than its factorization.

181681399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1698064.

The product of its digits is 93312, while the sum is 46.

The square root of 181681399 is about 13478.9242523282. The cubic root of 181681399 is about 566.3742348510.

The spelling of 181681399 in words is "one hundred eighty-one million, six hundred eighty-one thousand, three hundred ninety-nine".