1815874561 has 4 divisors (see below), whose sum is σ = 1815959812. Its totient is φ = 1815789312.

The previous prime is 1815874559. The next prime is 1815874573. The reversal of 1815874561 is 1654785181.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1780840000 + 35034561 = 42200^2 + 5919^2 .

It is a cyclic number.

It is not a de Polignac number, because 1815874561 - 2¹ = 1815874559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1815874531) 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, 19801 + ... + 63433.

It is an arithmetic number, because the mean of its divisors is an integer number (453989953).

Almost surely, 2^1815874561 is an apocalyptic number.

It is an amenable number.

1815874561 is a deficient number, since it is larger than the sum of its proper divisors (85251).

1815874561 is an equidigital number, since it uses as much as digits as its factorization.

1815874561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85250.

The product of its digits is 268800, while the sum is 46.

The square root of 1815874561 is about 42613.0796939156. The cubic root of 1815874561 is about 1220.0059484168.

The spelling of 1815874561 in words is "one billion, eight hundred fifteen million, eight hundred seventy-four thousand, five hundred sixty-one".