18555409 has 2 divisors, whose sum is σ = 18555410. Its totient is φ = 18555408.

The previous prime is 18555401. The next prime is 18555413. The reversal of 18555409 is 90455581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18037009 + 518400 = 4247^2 + 720^2 .

It is an emirp because it is prime and its reverse (90455581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18555409 - 2³ = 18555401 is a prime.

It is not a weakly prime, because it can be changed into another prime (18555401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9277704 + 9277705.

It is an arithmetic number, because the mean of its divisors is an integer number (9277705).

Almost surely, 2^18555409 is an apocalyptic number.

It is an amenable number.

18555409 is a deficient number, since it is larger than the sum of its proper divisors (1).

18555409 is an equidigital number, since it uses as much as digits as its factorization.

18555409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36000, while the sum is 37.

The square root of 18555409 is about 4307.5989831924. The cubic root of 18555409 is about 264.7424054344.

The spelling of 18555409 in words is "eighteen million, five hundred fifty-five thousand, four hundred nine".