181181993 has 4 divisors (see below), whose sum is σ = 185601108. Its totient is φ = 176762880.

The previous prime is 181181983. The next prime is 181181999. The reversal of 181181993 is 399181181.

181181993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 399181181 = 7 ⋅57025883.

It can be written as a sum of positive squares in 2 ways, for example, as 88868329 + 92313664 = 9427^2 + 9608^2 .

It is a cyclic number.

It is not a de Polignac number, because 181181993 - 2¹⁴ = 181165609 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 4419073 = 181181993 / (1 + 8 + 1 + 1 + 8 + 1 + 9 + 9 + 3).

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 181181993.

It is not an unprimeable number, because it can be changed into a prime (181181999) 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, 2209496 + ... + 2209577.

It is an arithmetic number, because the mean of its divisors is an integer number (46400277).

Almost surely, 2^181181993 is an apocalyptic number.

It is an amenable number.

181181993 is a deficient number, since it is larger than the sum of its proper divisors (4419115).

181181993 is an equidigital number, since it uses as much as digits as its factorization.

181181993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4419114.

The product of its digits is 15552, while the sum is 41.

The square root of 181181993 is about 13460.3860642999. The cubic root of 181181993 is about 565.8548086174.

The spelling of 181181993 in words is "one hundred eighty-one million, one hundred eighty-one thousand, nine hundred ninety-three".