181531213 has 8 divisors (see below), whose sum is σ = 192867480. Its totient is φ = 170533440.

The previous prime is 181531193. The next prime is 181531243. The reversal of 181531213 is 312135181.

It can be written as a sum of positive squares in 4 ways, for example, as 31787044 + 149744169 = 5638^2 + 12237^2 .

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 181531213 - 2²⁵ = 147976781 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 (181531243) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 83518 + ... + 85663.

It is an arithmetic number, because the mean of its divisors is an integer number (24108435).

Almost surely, 2^181531213 is an apocalyptic number.

It is an amenable number.

181531213 is a deficient number, since it is larger than the sum of its proper divisors (11336267).

181531213 is a wasteful number, since it uses less digits than its factorization.

181531213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169247.

The product of its digits is 720, while the sum is 25.

The square root of 181531213 is about 13473.3519585885. The cubic root of 181531213 is about 566.2181283726.

Adding to 181531213 its reverse (312135181), we get a palindrome (493666394).

The spelling of 181531213 in words is "one hundred eighty-one million, five hundred thirty-one thousand, two hundred thirteen".