820681 has 2 divisors, whose sum is σ = 820682. Its totient is φ = 820680.

The previous prime is 820679. The next prime is 820691. The reversal of 820681 is 186028.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 512656 + 308025 = 716^2 + 555^2 .

It is a cyclic number.

It is not a de Polignac number, because 820681 - 2¹ = 820679 is a prime.

It is a super-2 number, since 2×820681² = 1347034607522, which contains 22 as substring.

Together with 820679, it forms a pair of twin primes.

820681 is a lucky number.

It is a nialpdrome in base 7.

It is not a weakly prime, because it can be changed into another prime (820691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410340 + 410341.

It is an arithmetic number, because the mean of its divisors is an integer number (410341).

2⁸²⁰⁶⁸¹ is an apocalyptic number.

It is an amenable number.

820681 is a deficient number, since it is larger than the sum of its proper divisors (1).

820681 is an equidigital number, since it uses as much as digits as its factorization.

820681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 820681 is about 905.9144551226. The cubic root of 820681 is about 93.6249200090.

The spelling of 820681 in words is "eight hundred twenty thousand, six hundred eighty-one".