1815300823561 has 3 divisors (see below), whose sum is σ = 1815302170893. Its totient is φ = 1815299476230.

The previous prime is 1815300823541. The next prime is 1815300823591. The reversal of 1815300823561 is 1653280035181.

It is a happy number.

The square root of 1815300823561 is 1347331.

It is a perfect power (a square), and thus also a powerful number.

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 is not a de Polignac number, because 1815300823561 - 2⁵ = 1815300823529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1815300823541) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 673666 + ... + 2020996.

It is an arithmetic number, because the mean of its divisors is an integer number (605100723631).

Almost surely, 2^{1815300823561} is an apocalyptic number.

1815300823561 is the 1347331-st square number.

1815300823561 is the 673666-th centered octagonal number.

It is an amenable number.

1815300823561 is a deficient number, since it is larger than the sum of its proper divisors (1347332).

1815300823561 is an frugal number, since it uses more digits than its factorization.

1815300823561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2694662 (or 1347331 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 43.

The spelling of 1815300823561 in words is "one trillion, eight hundred fifteen billion, three hundred million, eight hundred twenty-three thousand, five hundred sixty-one".