817232653921 has 4 divisors (see below), whose sum is σ = 817284852244. Its totient is φ = 817180455600.

The previous prime is 817232653907. The next prime is 817232653957. The reversal of 817232653921 is 129356232718.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 129356232718 = 2 ⋅64678116359.

It can be written as a sum of positive squares in 2 ways, for example, as 801597902400 + 15634751521 = 895320^2 + 125039^2 .

It is a cyclic number.

It is not a de Polignac number, because 817232653921 - 2⁷ = 817232653793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (817232653021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26075670 + ... + 26106991.

It is an arithmetic number, because the mean of its divisors is an integer number (204321213061).

Almost surely, 2^817232653921 is an apocalyptic number.

It is an amenable number.

817232653921 is a deficient number, since it is larger than the sum of its proper divisors (52198323).

817232653921 is a wasteful number, since it uses less digits than its factorization.

817232653921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52198322.

The product of its digits is 1088640, while the sum is 49.

The spelling of 817232653921 in words is "eight hundred seventeen billion, two hundred thirty-two million, six hundred fifty-three thousand, nine hundred twenty-one".