18735721405 has 4 divisors (see below), whose sum is σ = 22482865692. Its totient is φ = 14988577120.

The previous prime is 18735721397. The next prime is 18735721421. The reversal of 18735721405 is 50412753781.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50412753781 = 13 ⋅3877904137.

It can be written as a sum of positive squares in 2 ways, for example, as 10718667961 + 8017053444 = 103531^2 + 89538^2 .

It is not a de Polignac number, because 18735721405 - 2³ = 18735721397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1873572136 + ... + 1873572145.

It is an arithmetic number, because the mean of its divisors is an integer number (5620716423).

Almost surely, 2^18735721405 is an apocalyptic number.

It is an amenable number.

18735721405 is a deficient number, since it is larger than the sum of its proper divisors (3747144287).

18735721405 is an equidigital number, since it uses as much as digits as its factorization.

18735721405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3747144286.

The product of its (nonzero) digits is 235200, while the sum is 43.

The spelling of 18735721405 in words is "eighteen billion, seven hundred thirty-five million, seven hundred twenty-one thousand, four hundred five".