81637 has 2 divisors, whose sum is σ = 81638. Its totient is φ = 81636.

The previous prime is 81629. The next prime is 81647. The reversal of 81637 is 73618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75076 + 6561 = 274^2 + 81^2 .

It is a cyclic number.

It is not a de Polignac number, because 81637 - 2³ = 81629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40818 + 40819.

It is an arithmetic number, because the mean of its divisors is an integer number (40819).

2⁸¹⁶³⁷ is an apocalyptic number.

It is an amenable number.

81637 is a deficient number, since it is larger than the sum of its proper divisors (1).

81637 is an equidigital number, since it uses as much as digits as its factorization.

81637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 25.

The square root of 81637 is about 285.7218927559. The cubic root of 81637 is about 43.3806124339.

The spelling of 81637 in words is "eighty-one thousand, six hundred thirty-seven".