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81649 is a prime number
BaseRepresentation
bin10011111011110001
311011000001
4103323301
510103044
61430001
7460021
oct237361
9134001
1081649
1156387
123b301
132b219
1421a81
15192d4
hex13ef1

81649 has 2 divisors, whose sum is σ = 81650. Its totient is φ = 81648.

The previous prime is 81647. The next prime is 81667. The reversal of 81649 is 94618.

81649 is nontrivially palindromic in base 4.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78400 + 3249 = 280^2 + 57^2 .

It is a cyclic number.

It is not a de Polignac number, because 81649 - 21 = 81647 is a prime.

Together with 81647, it forms a pair of twin primes.

81649 is a lucky 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, 40824 + 40825.

It is an arithmetic number, because the mean of its divisors is an integer number (40825).

281649 is an apocalyptic number.

It is an amenable number.

81649 is a deficient number, since it is larger than the sum of its proper divisors (1).

81649 is an equidigital number, since it uses as much as digits as its factorization.

81649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 28.

The square root of 81649 is about 285.7428914251. The cubic root of 81649 is about 43.3827378666.

The spelling of 81649 in words is "eighty-one thousand, six hundred forty-nine".