817211665 has 4 divisors (see below), whose sum is σ = 980654004. Its totient is φ = 653769328.

The previous prime is 817211653. The next prime is 817211699. The reversal of 817211665 is 566112718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566112718 = 2 ⋅283056359.

It can be written as a sum of positive squares in 2 ways, for example, as 477509904 + 339701761 = 21852^2 + 18431^2 .

It is a cyclic number.

It is not a de Polignac number, because 817211665 - 2¹³ = 817203473 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 in 3 ways as a sum of consecutive naturals, for example, 81721162 + ... + 81721171.

It is an arithmetic number, because the mean of its divisors is an integer number (245163501).

Almost surely, 2^817211665 is an apocalyptic number.

It is an amenable number.

817211665 is a deficient number, since it is larger than the sum of its proper divisors (163442339).

817211665 is a wasteful number, since it uses less digits than its factorization.

817211665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163442338.

The product of its digits is 20160, while the sum is 37.

The square root of 817211665 is about 28586.9142266177. The cubic root of 817211665 is about 934.9280412083.

The spelling of 817211665 in words is "eight hundred seventeen million, two hundred eleven thousand, six hundred sixty-five".