820618406261 has 2 divisors, whose sum is σ = 820618406262. Its totient is φ = 820618406260.

The previous prime is 820618406173. The next prime is 820618406317. The reversal of 820618406261 is 162604816028.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 808211788036 + 12406618225 = 899006^2 + 111385^2 .

It is a cyclic number.

It is not a de Polignac number, because 820618406261 - 2¹⁸ = 820618144117 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820618406161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410309203130 + 410309203131.

It is an arithmetic number, because the mean of its divisors is an integer number (410309203131).

Almost surely, 2^820618406261 is an apocalyptic number.

It is an amenable number.

820618406261 is a deficient number, since it is larger than the sum of its proper divisors (1).

820618406261 is an equidigital number, since it uses as much as digits as its factorization.

820618406261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 221184, while the sum is 44.

The spelling of 820618406261 in words is "eight hundred twenty billion, six hundred eighteen million, four hundred six thousand, two hundred sixty-one".