81213231 has 16 divisors (see below), whose sum is σ = 118320768. Its totient is φ = 49140000.

The previous prime is 81213229. The next prime is 81213263. The reversal of 81213231 is 13231218.

It is not a de Polignac number, because 81213231 - 2¹ = 81213229 is a prime.

It is a super-2 number, since 2×81213231² = 13191177778918722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81213198 and 81213207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81213221) 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 15 ways as a sum of consecutive naturals, for example, 23356 + ... + 26606.

It is an arithmetic number, because the mean of its divisors is an integer number (7395048).

Almost surely, 2^81213231 is an apocalyptic number.

81213231 is a deficient number, since it is larger than the sum of its proper divisors (37107537).

81213231 is a wasteful number, since it uses less digits than its factorization.

81213231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4022.

The product of its digits is 288, while the sum is 21.

The square root of 81213231 is about 9011.8383807079. The cubic root of 81213231 is about 433.0542079495.

Adding to 81213231 its reverse (13231218), we get a palindrome (94444449).

It can be divided in two parts, 81 and 213231, that added together give a palindrome (213312).

The spelling of 81213231 in words is "eighty-one million, two hundred thirteen thousand, two hundred thirty-one".