20857278918529 has 3 divisors (see below), whose sum is σ = 20857283485507. Its totient is φ = 20857274351552.

The previous prime is 20857278918491. The next prime is 20857278918559. The reversal of 20857278918529 is 92581987275802.

The square root of 20857278918529 is 4566977.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1993475729025 + 18863803189504 = 1411905^2 + 4343248^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20857278918529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20857278918559) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2283489 + ... + 6850465.

Almost surely, 2^{20857278918529} is an apocalyptic number.

20857278918529 is the 4566977-th square number.

20857278918529 is the 2283489-th centered octagonal number.

It is an amenable number.

20857278918529 is a deficient number, since it is larger than the sum of its proper divisors (4566978).

20857278918529 is an frugal number, since it uses more digits than its factorization.

20857278918529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9133954 (or 4566977 counting only the distinct ones).

The product of its (nonzero) digits is 406425600, while the sum is 73.

The spelling of 20857278918529 in words is "twenty trillion, eight hundred fifty-seven billion, two hundred seventy-eight million, nine hundred eighteen thousand, five hundred twenty-nine".