20517101243 has 4 divisors (see below), whose sum is σ = 20953635360. Its totient is φ = 20080567128.

The previous prime is 20517101233. The next prime is 20517101257. The reversal of 20517101243 is 34210171502.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20517101243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20517101233) 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, 218266988 + ... + 218267081.

It is an arithmetic number, because the mean of its divisors is an integer number (5238408840).

Almost surely, 2^20517101243 is an apocalyptic number.

20517101243 is a deficient number, since it is larger than the sum of its proper divisors (436534117).

20517101243 is an equidigital number, since it uses as much as digits as its factorization.

20517101243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 436534116.

The product of its (nonzero) digits is 1680, while the sum is 26.

Adding to 20517101243 its reverse (34210171502), we get a palindrome (54727272745).

The spelling of 20517101243 in words is "twenty billion, five hundred seventeen million, one hundred one thousand, two hundred forty-three".