81122781 has 8 divisors (see below), whose sum is σ = 108459904. Its totient is φ = 53933760.

The previous prime is 81122779. The next prime is 81122791. The reversal of 81122781 is 18722118.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81122781 - 2¹ = 81122779 is a prime.

It is a super-2 number, since 2×81122781² = 13161811194347922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81122711) 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 7 ways as a sum of consecutive naturals, for example, 35740 + ... + 37941.

It is an arithmetic number, because the mean of its divisors is an integer number (13557488).

Almost surely, 2^81122781 is an apocalyptic number.

It is an amenable number.

81122781 is a deficient number, since it is larger than the sum of its proper divisors (27337123).

81122781 is a wasteful number, since it uses less digits than its factorization.

81122781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74051.

The product of its digits is 1792, while the sum is 30.

The square root of 81122781 is about 9006.8185837176. The cubic root of 81122781 is about 432.8933790501.

Adding to 81122781 its reverse (18722118), we get a palindrome (99844899).

The spelling of 81122781 in words is "eighty-one million, one hundred twenty-two thousand, seven hundred eighty-one".