820949317681 has 2 divisors, whose sum is σ = 820949317682. Its totient is φ = 820949317680.

The previous prime is 820949317631. The next prime is 820949317709. The reversal of 820949317681 is 186713949028.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 753005682081 + 67943635600 = 867759^2 + 260660^2 .

It is a cyclic number.

It is not a de Polignac number, because 820949317681 - 2¹⁵ = 820949284913 is a prime.

It is a super-2 number, since 2×820949317681² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (820949317621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410474658840 + 410474658841.

It is an arithmetic number, because the mean of its divisors is an integer number (410474658841).

Almost surely, 2^820949317681 is an apocalyptic number.

It is an amenable number.

820949317681 is a deficient number, since it is larger than the sum of its proper divisors (1).

820949317681 is an equidigital number, since it uses as much as digits as its factorization.

820949317681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5225472, while the sum is 58.

The spelling of 820949317681 in words is "eight hundred twenty billion, nine hundred forty-nine million, three hundred seventeen thousand, six hundred eighty-one".