20501668505 has 4 divisors (see below), whose sum is σ = 24602002212. Its totient is φ = 16401334800.

The previous prime is 20501668501. The next prime is 20501668531. The reversal of 20501668505 is 50586610502.

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 11089564249 + 9412104256 = 105307^2 + 97016^2 .

It is not a de Polignac number, because 20501668505 - 2² = 20501668501 is a prime.

It is a super-2 number, since 2×20501668505² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20501668501) by changing a digit.

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, 2050166846 + ... + 2050166855.

It is an arithmetic number, because the mean of its divisors is an integer number (6150500553).

Almost surely, 2^20501668505 is an apocalyptic number.

It is an amenable number.

20501668505 is a deficient number, since it is larger than the sum of its proper divisors (4100333707).

20501668505 is an equidigital number, since it uses as much as digits as its factorization.

20501668505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4100333706.

The product of its (nonzero) digits is 72000, while the sum is 38.

The spelling of 20501668505 in words is "twenty billion, five hundred one million, six hundred sixty-eight thousand, five hundred five".