18915565 has 4 divisors (see below), whose sum is σ = 22698684. Its totient is φ = 15132448.

The previous prime is 18915553. The next prime is 18915581. The reversal of 18915565 is 56551981.

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 6985449 + 11930116 = 2643^2 + 3454^2 .

It is a cyclic number.

It is not a de Polignac number, because 18915565 - 2²¹ = 16818413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1891552 + ... + 1891561.

It is an arithmetic number, because the mean of its divisors is an integer number (5674671).

Almost surely, 2^18915565 is an apocalyptic number.

It is an amenable number.

18915565 is a deficient number, since it is larger than the sum of its proper divisors (3783119).

18915565 is an equidigital number, since it uses as much as digits as its factorization.

18915565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3783118.

The product of its digits is 54000, while the sum is 40.

The square root of 18915565 is about 4349.2028005141. The cubic root of 18915565 is about 266.4443033464. Note that the first 3 decimals are identical.

The spelling of 18915565 in words is "eighteen million, nine hundred fifteen thousand, five hundred sixty-five".