18411721 has 2 divisors, whose sum is σ = 18411722. Its totient is φ = 18411720.

The previous prime is 18411689. The next prime is 18411727. The reversal of 18411721 is 12711481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13286025 + 5125696 = 3645^2 + 2264^2 .

It is an emirp because it is prime and its reverse (12711481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18411721 - 2⁵ = 18411689 is a prime.

It is not a weakly prime, because it can be changed into another prime (18411727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9205860 + 9205861.

It is an arithmetic number, because the mean of its divisors is an integer number (9205861).

Almost surely, 2^18411721 is an apocalyptic number.

It is an amenable number.

18411721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18411721 is an equidigital number, since it uses as much as digits as its factorization.

18411721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 448, while the sum is 25.

The square root of 18411721 is about 4290.8881365051. Note that the first 3 decimals coincide. The cubic root of 18411721 is about 264.0572696769.

The spelling of 18411721 in words is "eighteen million, four hundred eleven thousand, seven hundred twenty-one".