181391989 has 8 divisors (see below), whose sum is σ = 192456000. Its totient is φ = 170371776.

The previous prime is 181391971. The next prime is 181391999. The reversal of 181391989 is 989193181.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 181391989 - 2⁵ = 181391957 is a prime.

It is a super-2 number, since 2×181391989² = 65806107346752242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (181391939) 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 7 ways as a sum of consecutive naturals, for example, 2209 + ... + 19174.

It is an arithmetic number, because the mean of its divisors is an integer number (24057000).

Almost surely, 2^181391989 is an apocalyptic number.

It is an amenable number.

181391989 is a deficient number, since it is larger than the sum of its proper divisors (11064011).

181391989 is a wasteful number, since it uses less digits than its factorization.

181391989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21899.

The product of its digits is 139968, while the sum is 49.

The square root of 181391989 is about 13468.1843245480. The cubic root of 181391989 is about 566.0733391047.

The spelling of 181391989 in words is "one hundred eighty-one million, three hundred ninety-one thousand, nine hundred eighty-nine".