20815241658817 has 4 divisors (see below), whose sum is σ = 20816054748036. Its totient is φ = 20814428569600.

The previous prime is 20815241658767. The next prime is 20815241658853. The reversal of 20815241658817 is 71885614251802.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10353406664241 + 10461834994576 = 3217671^2 + 3234476^2 .

It is a cyclic number.

It is not a de Polignac number, because 20815241658817 - 2⁴³ = 12019148636609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20815241658857) 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, 406506208 + ... + 406557409.

It is an arithmetic number, because the mean of its divisors is an integer number (5204013687009).

Almost surely, 2^{20815241658817} is an apocalyptic number.

It is an amenable number.

20815241658817 is a deficient number, since it is larger than the sum of its proper divisors (813089219).

20815241658817 is an equidigital number, since it uses as much as digits as its factorization.

20815241658817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 813089218.

The product of its (nonzero) digits is 8601600, while the sum is 58.

The spelling of 20815241658817 in words is "twenty trillion, eight hundred fifteen billion, two hundred forty-one million, six hundred fifty-eight thousand, eight hundred seventeen".