81221131 has 4 divisors (see below), whose sum is σ = 81242392. Its totient is φ = 81199872.

The previous prime is 81221117. The next prime is 81221159. The reversal of 81221131 is 13112218.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81221131 - 2⁵ = 81221099 is a prime.

It is a super-2 number, since 2×81221131² = 13193744241838322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81221099 and 81221108.

It is not an unprimeable number, because it can be changed into a prime (81221191) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3141 + ... + 13126.

It is an arithmetic number, because the mean of its divisors is an integer number (20310598).

Almost surely, 2^81221131 is an apocalyptic number.

81221131 is a deficient number, since it is larger than the sum of its proper divisors (21261).

81221131 is a wasteful number, since it uses less digits than its factorization.

81221131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21260.

The product of its digits is 96, while the sum is 19.

The square root of 81221131 is about 9012.2766823927. The cubic root of 81221131 is about 433.0682492466.

Adding to 81221131 its reverse (13112218), we get a palindrome (94333349).

The spelling of 81221131 in words is "eighty-one million, two hundred twenty-one thousand, one hundred thirty-one".