18019945 has 4 divisors (see below), whose sum is σ = 21623940. Its totient is φ = 14415952.

The previous prime is 18019943. The next prime is 18019993. The reversal of 18019945 is 54991081.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54991081 = 47 ⋅1170023.

It can be written as a sum of positive squares in 2 ways, for example, as 9511056 + 8508889 = 3084^2 + 2917^2 .

It is a cyclic number.

It is not a de Polignac number, because 18019945 - 2¹ = 18019943 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18019943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1801990 + ... + 1801999.

It is an arithmetic number, because the mean of its divisors is an integer number (5405985).

Almost surely, 2^18019945 is an apocalyptic number.

It is an amenable number.

18019945 is a deficient number, since it is larger than the sum of its proper divisors (3603995).

18019945 is an equidigital number, since it uses as much as digits as its factorization.

18019945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3603994.

The product of its (nonzero) digits is 12960, while the sum is 37.

The square root of 18019945 is about 4244.9905771391. The cubic root of 18019945 is about 262.1709012592.

The spelling of 18019945 in words is "eighteen million, nineteen thousand, nine hundred forty-five".