81213 has 16 divisors (see below), whose sum is σ = 124416. Its totient is φ = 46640.

The previous prime is 81203. The next prime is 81223. The reversal of 81213 is 31218.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81203) and next prime (81223).

It is not a de Polignac number, because 81213 - 2⁴ = 81197 is a prime.

It is a super-4 number, since 4×81213⁴ (a number of 21 digits) contains 4444 as substring.

81213 is a lucky number.

It is a plaindrome in base 9.

It is a junction number, because it is equal to n+sod(n) for n = 81192 and 81201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 706 + ... + 812.

It is an arithmetic number, because the mean of its divisors is an integer number (7776).

2⁸¹²¹³ is an apocalyptic number.

It is an amenable number.

81213 is a deficient number, since it is larger than the sum of its proper divisors (43203).

81213 is a wasteful number, since it uses less digits than its factorization.

81213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144.

The product of its digits is 48, while the sum is 15.

The square root of 81213 is about 284.9789465908. The cubic root of 81213 is about 43.3053797361.

It can be divided in two parts, 8 and 1213, that added together give a palindrome (1221).

The spelling of 81213 in words is "eighty-one thousand, two hundred thirteen".