20518249877 has 4 divisors (see below), whose sum is σ = 20518915020. Its totient is φ = 20517584736.

The previous prime is 20518249849. The next prime is 20518249901. The reversal of 20518249877 is 77894281502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 77894281502 = 2 ⋅38947140751.

It can be written as a sum of positive squares in 2 ways, for example, as 7256654596 + 13261595281 = 85186^2 + 115159^2 .

It is a cyclic number.

It is not a de Polignac number, because 20518249877 - 2¹⁰ = 20518248853 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 (20518240877) 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, 283928 + ... + 348785.

It is an arithmetic number, because the mean of its divisors is an integer number (5129728755).

Almost surely, 2^20518249877 is an apocalyptic number.

It is an amenable number.

20518249877 is a deficient number, since it is larger than the sum of its proper divisors (665143).

20518249877 is an equidigital number, since it uses as much as digits as its factorization.

20518249877 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665142.

The product of its (nonzero) digits is 2257920, while the sum is 53.

The spelling of 20518249877 in words is "twenty billion, five hundred eighteen million, two hundred forty-nine thousand, eight hundred seventy-seven".