81549725429 has 2 divisors, whose sum is σ = 81549725430. Its totient is φ = 81549725428.

The previous prime is 81549725423. The next prime is 81549725473. The reversal of 81549725429 is 92452794518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81527380900 + 22344529 = 285530^2 + 4727^2 .

It is a cyclic number.

It is not a de Polignac number, because 81549725429 - 2¹² = 81549721333 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81549725423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40774862714 + 40774862715.

It is an arithmetic number, because the mean of its divisors is an integer number (40774862715).

Almost surely, 2^81549725429 is an apocalyptic number.

It is an amenable number.

81549725429 is a deficient number, since it is larger than the sum of its proper divisors (1).

81549725429 is an equidigital number, since it uses as much as digits as its factorization.

81549725429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7257600, while the sum is 56.

The spelling of 81549725429 in words is "eighty-one billion, five hundred forty-nine million, seven hundred twenty-five thousand, four hundred twenty-nine".