20857680605 has 4 divisors (see below), whose sum is σ = 25029216732. Its totient is φ = 16686144480.

The previous prime is 20857680583. The next prime is 20857680607. The reversal of 20857680605 is 50608675802.

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 12733542649 + 8124137956 = 112843^2 + 90134^2 .

It is not a de Polignac number, because 20857680605 - 2²⁰ = 20856632029 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20857680605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20857680607) 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, 2085768056 + ... + 2085768065.

It is an arithmetic number, because the mean of its divisors is an integer number (6257304183).

Almost surely, 2^20857680605 is an apocalyptic number.

It is an amenable number.

20857680605 is a deficient number, since it is larger than the sum of its proper divisors (4171536127).

20857680605 is an equidigital number, since it uses as much as digits as its factorization.

20857680605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4171536126.

The product of its (nonzero) digits is 806400, while the sum is 47.

The spelling of 20857680605 in words is "twenty billion, eight hundred fifty-seven million, six hundred eighty thousand, six hundred five".