81859549 has 2 divisors, whose sum is σ = 81859550. Its totient is φ = 81859548.

The previous prime is 81859537. The next prime is 81859579. The reversal of 81859549 is 94595818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81812025 + 47524 = 9045^2 + 218^2 .

It is a cyclic number.

It is not a de Polignac number, because 81859549 - 2¹⁷ = 81728477 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81859529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40929774 + 40929775.

It is an arithmetic number, because the mean of its divisors is an integer number (40929775).

Almost surely, 2^81859549 is an apocalyptic number.

It is an amenable number.

81859549 is a deficient number, since it is larger than the sum of its proper divisors (1).

81859549 is an equidigital number, since it uses as much as digits as its factorization.

81859549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 518400, while the sum is 49.

The square root of 81859549 is about 9047.6267053852. The cubic root of 81859549 is about 434.1999634222.

The spelling of 81859549 in words is "eighty-one million, eight hundred fifty-nine thousand, five hundred forty-nine".