81122221 has 4 divisors (see below), whose sum is σ = 81714492. Its totient is φ = 80529952.

The previous prime is 81122213. The next prime is 81122273. The reversal of 81122221 is 12222118.

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

It can be written as a sum of positive squares in 2 ways, for example, as 67059721 + 14062500 = 8189^2 + 3750^2 .

It is a cyclic number.

It is not a de Polignac number, because 81122221 - 2³ = 81122213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81122201) 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, 295930 + ... + 296203.

It is an arithmetic number, because the mean of its divisors is an integer number (20428623).

Almost surely, 2^81122221 is an apocalyptic number.

It is an amenable number.

81122221 is a deficient number, since it is larger than the sum of its proper divisors (592271).

81122221 is a wasteful number, since it uses less digits than its factorization.

81122221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592270.

The product of its digits is 128, while the sum is 19.

The square root of 81122221 is about 9006.7874961054. The cubic root of 81122221 is about 432.8923829433.

Adding to 81122221 its reverse (12222118), we get a palindrome (93344339).

It can be divided in two parts, 811 and 22221, that added together give a palindrome (23032).

The spelling of 81122221 in words is "eighty-one million, one hundred twenty-two thousand, two hundred twenty-one".