20518370221757 has 4 divisors (see below), whose sum is σ = 21725333175996. Its totient is φ = 19311407267520.

The previous prime is 20518370221733. The next prime is 20518370221787. The reversal of 20518370221757 is 75712207381502.

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 12784264609081 + 7734105612676 = 3575509^2 + 2781026^2 .

It is a cyclic number.

It is not a de Polignac number, because 20518370221757 - 2²⁶ = 20518303112893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20518370221787) 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, 603481477094 + ... + 603481477127.

It is an arithmetic number, because the mean of its divisors is an integer number (5431333293999).

Almost surely, 2^{20518370221757} is an apocalyptic number.

It is an amenable number.

20518370221757 is a deficient number, since it is larger than the sum of its proper divisors (1206962954239).

20518370221757 is a wasteful number, since it uses less digits than its factorization.

20518370221757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206962954238.

The product of its (nonzero) digits is 1646400, while the sum is 50.

The spelling of 20518370221757 in words is "twenty trillion, five hundred eighteen billion, three hundred seventy million, two hundred twenty-one thousand, seven hundred fifty-seven".