81686321 has 2 divisors, whose sum is σ = 81686322. Its totient is φ = 81686320.

The previous prime is 81686299. The next prime is 81686347. The reversal of 81686321 is 12368618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56325025 + 25361296 = 7505^2 + 5036^2 .

It is a cyclic number.

It is not a de Polignac number, because 81686321 - 2¹⁰ = 81685297 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81686351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40843160 + 40843161.

It is an arithmetic number, because the mean of its divisors is an integer number (40843161).

Almost surely, 2^81686321 is an apocalyptic number.

It is an amenable number.

81686321 is a deficient number, since it is larger than the sum of its proper divisors (1).

81686321 is an equidigital number, since it uses as much as digits as its factorization.

81686321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 35.

The square root of 81686321 is about 9038.0485172409. The cubic root of 81686321 is about 433.8934680866.

The spelling of 81686321 in words is "eighty-one million, six hundred eighty-six thousand, three hundred twenty-one".