815765620421 has 2 divisors, whose sum is σ = 815765620422. Its totient is φ = 815765620420.

The previous prime is 815765620393. The next prime is 815765620429. The reversal of 815765620421 is 124026567518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 424497856225 + 391267764196 = 651535^2 + 625514^2 .

It is a cyclic number.

It is not a de Polignac number, because 815765620421 - 2¹⁰ = 815765619397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (815765620429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407882810210 + 407882810211.

It is an arithmetic number, because the mean of its divisors is an integer number (407882810211).

Almost surely, 2^815765620421 is an apocalyptic number.

It is an amenable number.

815765620421 is a deficient number, since it is larger than the sum of its proper divisors (1).

815765620421 is an equidigital number, since it uses as much as digits as its factorization.

815765620421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 806400, while the sum is 47.

The spelling of 815765620421 in words is "eight hundred fifteen billion, seven hundred sixty-five million, six hundred twenty thousand, four hundred twenty-one".