820631681 has 2 divisors, whose sum is σ = 820631682. Its totient is φ = 820631680.

The previous prime is 820631627. The next prime is 820631689. The reversal of 820631681 is 186136028.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 762643456 + 57988225 = 27616^2 + 7615^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820631681 is a prime.

It is a super-2 number, since 2×820631681² = 1346872711721771522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (820631689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410315840 + 410315841.

It is an arithmetic number, because the mean of its divisors is an integer number (410315841).

Almost surely, 2^820631681 is an apocalyptic number.

It is an amenable number.

820631681 is a deficient number, since it is larger than the sum of its proper divisors (1).

820631681 is an equidigital number, since it uses as much as digits as its factorization.

820631681 is an odious number, because the sum of its binary digits is odd.

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

The square root of 820631681 is about 28646.6696319136. The cubic root of 820631681 is about 936.2304450156.

The spelling of 820631681 in words is "eight hundred twenty million, six hundred thirty-one thousand, six hundred eighty-one".