181221418 has 16 divisors (see below), whose sum is σ = 314599680. Its totient is φ = 76682736.

The previous prime is 181221407. The next prime is 181221419. The reversal of 181221418 is 814122181.

It is not an unprimeable number, because it can be changed into a prime (181221419) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 80821 + ... + 83032.

It is an arithmetic number, because the mean of its divisors is an integer number (19662480).

Almost surely, 2^181221418 is an apocalyptic number.

181221418 is a deficient number, since it is larger than the sum of its proper divisors (133378262).

181221418 is a wasteful number, since it uses less digits than its factorization.

181221418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163941.

The product of its digits is 1024, while the sum is 28.

The square root of 181221418 is about 13461.8504671535. The cubic root of 181221418 is about 565.8958487663.

Adding to 181221418 its reverse (814122181), we get a palindrome (995343599).

The spelling of 181221418 in words is "one hundred eighty-one million, two hundred twenty-one thousand, four hundred eighteen".