20505321355 has 4 divisors (see below), whose sum is σ = 24606385632. Its totient is φ = 16404257080.

The previous prime is 20505321329. The next prime is 20505321371. The reversal of 20505321355 is 55312350502.

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

It is not a de Polignac number, because 20505321355 - 2²⁹ = 19968450443 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2050532131 + ... + 2050532140.

It is an arithmetic number, because the mean of its divisors is an integer number (6151596408).

Almost surely, 2^20505321355 is an apocalyptic number.

20505321355 is a deficient number, since it is larger than the sum of its proper divisors (4101064277).

20505321355 is an equidigital number, since it uses as much as digits as its factorization.

20505321355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4101064276.

The product of its (nonzero) digits is 22500, while the sum is 31.

Adding to 20505321355 its reverse (55312350502), we get a palindrome (75817671857).

The spelling of 20505321355 in words is "twenty billion, five hundred five million, three hundred twenty-one thousand, three hundred fifty-five".