18500066721 has 24 divisors (see below), whose sum is σ = 27891002880. Its totient is φ = 11794248576.

The previous prime is 18500066707. The next prime is 18500066729. The reversal of 18500066721 is 12766000581.

It is not a de Polignac number, because 18500066721 - 2¹⁰ = 18500065697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18500066729) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1110985 + ... + 1127513.

It is an arithmetic number, because the mean of its divisors is an integer number (1162125120).

Almost surely, 2^18500066721 is an apocalyptic number.

It is an amenable number.

18500066721 is a deficient number, since it is larger than the sum of its proper divisors (9390936159).

18500066721 is a wasteful number, since it uses less digits than its factorization.

18500066721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21965 (or 21962 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The spelling of 18500066721 in words is "eighteen billion, five hundred million, sixty-six thousand, seven hundred twenty-one".