18623205721 has 2 divisors, whose sum is σ = 18623205722. Its totient is φ = 18623205720.

The previous prime is 18623205719. The next prime is 18623205749. The reversal of 18623205721 is 12750232681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11206551321 + 7416654400 = 105861^2 + 86120^2 .

It is an emirp because it is prime and its reverse (12750232681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18623205721 - 2¹ = 18623205719 is a prime.

Together with 18623205719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (18623205221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9311602860 + 9311602861.

It is an arithmetic number, because the mean of its divisors is an integer number (9311602861).

Almost surely, 2^18623205721 is an apocalyptic number.

It is an amenable number.

18623205721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18623205721 is an equidigital number, since it uses as much as digits as its factorization.

18623205721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40320, while the sum is 37.

The spelling of 18623205721 in words is "eighteen billion, six hundred twenty-three million, two hundred five thousand, seven hundred twenty-one".