18147385721 has 2 divisors, whose sum is σ = 18147385722. Its totient is φ = 18147385720.

The previous prime is 18147385717. The next prime is 18147385723. The reversal of 18147385721 is 12758374181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17891737600 + 255648121 = 133760^2 + 15989^2 .

It is a cyclic number.

It is not a de Polignac number, because 18147385721 - 2² = 18147385717 is a prime.

Together with 18147385723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18147385723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9073692860 + 9073692861.

It is an arithmetic number, because the mean of its divisors is an integer number (9073692861).

Almost surely, 2^18147385721 is an apocalyptic number.

It is an amenable number.

18147385721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18147385721 is an equidigital number, since it uses as much as digits as its factorization.

18147385721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 376320, while the sum is 47.

The spelling of 18147385721 in words is "eighteen billion, one hundred forty-seven million, three hundred eighty-five thousand, seven hundred twenty-one".