18724502921 has 4 divisors (see below), whose sum is σ = 18771197844. Its totient is φ = 18677808000.

The previous prime is 18724502917. The next prime is 18724502989. The reversal of 18724502921 is 12920542781.

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 18046160896 + 678342025 = 134336^2 + 26045^2 .

It is a cyclic number.

It is not a de Polignac number, because 18724502921 - 2² = 18724502917 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18724502911) 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, 23346860 + ... + 23347661.

It is an arithmetic number, because the mean of its divisors is an integer number (4692799461).

Almost surely, 2^18724502921 is an apocalyptic number.

It is an amenable number.

18724502921 is a deficient number, since it is larger than the sum of its proper divisors (46694923).

18724502921 is an equidigital number, since it uses as much as digits as its factorization.

18724502921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46694922.

The product of its (nonzero) digits is 80640, while the sum is 41.

The spelling of 18724502921 in words is "eighteen billion, seven hundred twenty-four million, five hundred two thousand, nine hundred twenty-one".