81000121022021 has 4 divisors (see below), whose sum is σ = 83793228643500. Its totient is φ = 78207013400544.

The previous prime is 81000121021991. The next prime is 81000121022053. The reversal of 81000121022021 is 12022012100018.

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 64122698752225 + 16877422269796 = 8007665^2 + 4108214^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81000121022021 is a prime.

It is a super-2 number, since 2×81000121022021² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81000121021984 and 81000121022002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81000121022071) 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, 1396553810696 + ... + 1396553810753.

It is an arithmetic number, because the mean of its divisors is an integer number (20948307160875).

Almost surely, 2^{81000121022021} is an apocalyptic number.

It is an amenable number.

81000121022021 is a deficient number, since it is larger than the sum of its proper divisors (2793107621479).

81000121022021 is a wasteful number, since it uses less digits than its factorization.

81000121022021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2793107621478.

The product of its (nonzero) digits is 128, while the sum is 20.

Adding to 81000121022021 its reverse (12022012100018), we get a palindrome (93022133122039).

The spelling of 81000121022021 in words is "eighty-one trillion, one hundred twenty-one million, twenty-two thousand, twenty-one".