20451243561605 has 4 divisors (see below), whose sum is σ = 24541492273932. Its totient is φ = 16360994849280.

The previous prime is 20451243561563. The next prime is 20451243561607. The reversal of 20451243561605 is 50616534215402.

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 9946397671681 + 10504845889924 = 3153791^2 + 3241118^2 .

It is not a de Polignac number, because 20451243561605 - 2¹⁶ = 20451243496069 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 (20451243561607) 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, 2045124356156 + ... + 2045124356165.

It is an arithmetic number, because the mean of its divisors is an integer number (6135373068483).

Almost surely, 2^{20451243561605} is an apocalyptic number.

It is an amenable number.

20451243561605 is a deficient number, since it is larger than the sum of its proper divisors (4090248712327).

20451243561605 is an equidigital number, since it uses as much as digits as its factorization.

20451243561605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4090248712326.

The product of its (nonzero) digits is 864000, while the sum is 44.

The spelling of 20451243561605 in words is "twenty trillion, four hundred fifty-one billion, two hundred forty-three million, five hundred sixty-one thousand, six hundred five".