81721624741 has 2 divisors, whose sum is σ = 81721624742. Its totient is φ = 81721624740.

The previous prime is 81721624739. The next prime is 81721624753. The reversal of 81721624741 is 14742612718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46928556900 + 34793067841 = 216630^2 + 186529^2 .

It is a cyclic number.

It is not a de Polignac number, because 81721624741 - 2¹ = 81721624739 is a prime.

It is a super-3 number, since 3×81721624741³ (a number of 34 digits) contains 333 as substring.

Together with 81721624739, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81721624441) 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 as a sum of consecutive naturals, namely, 40860812370 + 40860812371.

It is an arithmetic number, because the mean of its divisors is an integer number (40860812371).

Almost surely, 2^81721624741 is an apocalyptic number.

It is an amenable number.

81721624741 is a deficient number, since it is larger than the sum of its proper divisors (1).

81721624741 is an equidigital number, since it uses as much as digits as its factorization.

81721624741 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 150528, while the sum is 43.

The spelling of 81721624741 in words is "eighty-one billion, seven hundred twenty-one million, six hundred twenty-four thousand, seven hundred forty-one".