20643651405818 has 24 divisors (see below), whose sum is σ = 36033673700052. Its totient is φ = 8844182351424.

The previous prime is 20643651405791. The next prime is 20643651405821. The reversal of 20643651405818 is 81850415634602.

It can be written as a sum of positive squares in 2 ways, for example, as 17876043192049 + 2767608213769 = 4228007^2 + 1663613^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 20643651405818.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36585521 + ... + 37145492.

Almost surely, 2^{20643651405818} is an apocalyptic number.

20643651405818 is a deficient number, since it is larger than the sum of its proper divisors (15390022294234).

20643651405818 is a wasteful number, since it uses less digits than its factorization.

20643651405818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73733886 (or 73733879 counting only the distinct ones).

The product of its (nonzero) digits is 5529600, while the sum is 53.

The spelling of 20643651405818 in words is "twenty trillion, six hundred forty-three billion, six hundred fifty-one million, four hundred five thousand, eight hundred eighteen".