18539921 has 4 divisors (see below), whose sum is σ = 18664500. Its totient is φ = 18415344.

The previous prime is 18539879. The next prime is 18539933. The reversal of 18539921 is 12993581.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12993581 = 139 ⋅93479.

It can be written as a sum of positive squares in 2 ways, for example, as 1234321 + 17305600 = 1111^2 + 4160^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18539921 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18539951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62066 + ... + 62363.

It is an arithmetic number, because the mean of its divisors is an integer number (4666125).

Almost surely, 2^18539921 is an apocalyptic number.

It is an amenable number.

18539921 is a deficient number, since it is larger than the sum of its proper divisors (124579).

18539921 is a wasteful number, since it uses less digits than its factorization.

18539921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124578.

The product of its digits is 19440, while the sum is 38.

The square root of 18539921 is about 4305.8008546611. The cubic root of 18539921 is about 264.6687257195.

The spelling of 18539921 in words is "eighteen million, five hundred thirty-nine thousand, nine hundred twenty-one".