81340012921 has 4 divisors (see below), whose sum is σ = 81403710372. Its totient is φ = 81276315472.

The previous prime is 81340012913. The next prime is 81340012937. The reversal of 81340012921 is 12921004318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12921004318 = 2 ⋅6460502159.

It can be written as a sum of positive squares in 2 ways, for example, as 63607362025 + 17732650896 = 252205^2 + 133164^2 .

It is a cyclic number.

It is not a de Polignac number, because 81340012921 - 2³ = 81340012913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81340012991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 31846810 + ... + 31849363.

It is an arithmetic number, because the mean of its divisors is an integer number (20350927593).

Almost surely, 2^81340012921 is an apocalyptic number.

It is an amenable number.

81340012921 is a deficient number, since it is larger than the sum of its proper divisors (63697451).

81340012921 is a wasteful number, since it uses less digits than its factorization.

81340012921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63697450.

The product of its (nonzero) digits is 3456, while the sum is 31.

The spelling of 81340012921 in words is "eighty-one billion, three hundred forty million, twelve thousand, nine hundred twenty-one".