20505721717023 has 16 divisors (see below), whose sum is σ = 27933196767840. Its totient is φ = 13377530935296.

The previous prime is 20505721716983. The next prime is 20505721717043. The reversal of 20505721717023 is 32071712750502.

It is not a de Polignac number, because 20505721717023 - 2²¹ = 20505719619871 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20505721717043) 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 15 ways as a sum of consecutive naturals, for example, 395852740 + ... + 395904537.

It is an arithmetic number, because the mean of its divisors is an integer number (1745824797990).

Almost surely, 2^{20505721717023} is an apocalyptic number.

20505721717023 is a deficient number, since it is larger than the sum of its proper divisors (7427475050817).

20505721717023 is an equidigital number, since it uses as much as digits as its factorization.

20505721717023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791757466.

The product of its (nonzero) digits is 205800, while the sum is 42.

The spelling of 20505721717023 in words is "twenty trillion, five hundred five billion, seven hundred twenty-one million, seven hundred seventeen thousand, twenty-three".