81811121 has 4 divisors (see below), whose sum is σ = 93498432. Its totient is φ = 70123812.

The previous prime is 81811109. The next prime is 81811141. The reversal of 81811121 is 12111818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12111818 = 2 ⋅6055909.

It is a cyclic number.

It is not a de Polignac number, because 81811121 - 2¹⁰ = 81810097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81811141) 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, 5843645 + ... + 5843658.

It is an arithmetic number, because the mean of its divisors is an integer number (23374608).

Almost surely, 2^81811121 is an apocalyptic number.

It is an amenable number.

81811121 is a deficient number, since it is larger than the sum of its proper divisors (11687311).

81811121 is a wasteful number, since it uses less digits than its factorization.

81811121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11687310.

The product of its digits is 128, while the sum is 23.

The square root of 81811121 is about 9044.9500275015. The cubic root of 81811121 is about 434.1143224919.

Adding to 81811121 its reverse (12111818), we get a palindrome (93922939).

The spelling of 81811121 in words is "eighty-one million, eight hundred eleven thousand, one hundred twenty-one".