81541549 has 2 divisors, whose sum is σ = 81541550. Its totient is φ = 81541548.

The previous prime is 81541547. The next prime is 81541553. The reversal of 81541549 is 94514518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46648900 + 34892649 = 6830^2 + 5907^2 .

It is a cyclic number.

It is not a de Polignac number, because 81541549 - 2¹ = 81541547 is a prime.

Together with 81541547, 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 (81541541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40770774 + 40770775.

It is an arithmetic number, because the mean of its divisors is an integer number (40770775).

Almost surely, 2^81541549 is an apocalyptic number.

It is an amenable number.

81541549 is a deficient number, since it is larger than the sum of its proper divisors (1).

81541549 is an equidigital number, since it uses as much as digits as its factorization.

81541549 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 28800, while the sum is 37.

The square root of 81541549 is about 9030.0359356982. The cubic root of 81541549 is about 433.6369878902.

The spelling of 81541549 in words is "eighty-one million, five hundred forty-one thousand, five hundred forty-nine".