18164016721 has 2 divisors, whose sum is σ = 18164016722. Its totient is φ = 18164016720.

The previous prime is 18164016671. The next prime is 18164016763. The reversal of 18164016721 is 12761046181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18004272400 + 159744321 = 134180^2 + 12639^2 .

It is a cyclic number.

It is not a de Polignac number, because 18164016721 - 2¹⁵ = 18163983953 is a prime.

It is not a weakly prime, because it can be changed into another prime (18164016781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9082008360 + 9082008361.

It is an arithmetic number, because the mean of its divisors is an integer number (9082008361).

Almost surely, 2^18164016721 is an apocalyptic number.

It is an amenable number.

18164016721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18164016721 is an equidigital number, since it uses as much as digits as its factorization.

18164016721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 37.

The spelling of 18164016721 in words is "eighteen billion, one hundred sixty-four million, sixteen thousand, seven hundred twenty-one".