18921865 has 4 divisors (see below), whose sum is σ = 22706244. Its totient is φ = 15137488.

The previous prime is 18921863. The next prime is 18921899. The reversal of 18921865 is 56812981.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7772944 + 11148921 = 2788^2 + 3339^2 .

It is a cyclic number.

It is not a de Polignac number, because 18921865 - 2¹ = 18921863 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18921863) 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, 1892182 + ... + 1892191.

It is an arithmetic number, because the mean of its divisors is an integer number (5676561).

Almost surely, 2^18921865 is an apocalyptic number.

It is an amenable number.

18921865 is a deficient number, since it is larger than the sum of its proper divisors (3784379).

18921865 is an equidigital number, since it uses as much as digits as its factorization.

18921865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3784378.

The product of its digits is 34560, while the sum is 40.

The square root of 18921865 is about 4349.9270108819. The cubic root of 18921865 is about 266.4738806246.

The spelling of 18921865 in words is "eighteen million, nine hundred twenty-one thousand, eight hundred sixty-five".