18945509 has 4 divisors (see below), whose sum is σ = 20667840. Its totient is φ = 17223180.

The previous prime is 18945503. The next prime is 18945529. The reversal of 18945509 is 90554981.

18945509 = 2512² + 2513² + 2514².

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18945509 - 2¹² = 18941413 is a prime.

It is a super-2 number, since 2×18945509² = 717864622538162, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18945503) 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 in 3 ways as a sum of consecutive naturals, for example, 861149 + ... + 861170.

It is an arithmetic number, because the mean of its divisors is an integer number (5166960).

Almost surely, 2^18945509 is an apocalyptic number.

It is an amenable number.

18945509 is a deficient number, since it is larger than the sum of its proper divisors (1722331).

18945509 is a wasteful number, since it uses less digits than its factorization.

18945509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1722330.

The product of its (nonzero) digits is 64800, while the sum is 41.

The square root of 18945509 is about 4352.6439091660. The cubic root of 18945509 is about 266.5848261008.

The spelling of 18945509 in words is "eighteen million, nine hundred forty-five thousand, five hundred nine".