1813080721 has 4 divisors (see below), whose sum is σ = 1857302244. Its totient is φ = 1768859200.

The previous prime is 1813080701. The next prime is 1813080727. The reversal of 1813080721 is 1270803181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1270803181 = 31 ⋅40993651.

It can be written as a sum of positive squares in 2 ways, for example, as 37638225 + 1775442496 = 6135^2 + 42136^2 .

It is a cyclic number.

It is not a de Polignac number, because 1813080721 - 2¹³ = 1813072529 is a prime.

It is a Smith number, since the sum of its digits (31) 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 (1813080727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22110700 + ... + 22110781.

It is an arithmetic number, because the mean of its divisors is an integer number (464325561).

Almost surely, 2^1813080721 is an apocalyptic number.

It is an amenable number.

1813080721 is a deficient number, since it is larger than the sum of its proper divisors (44221523).

1813080721 is an equidigital number, since it uses as much as digits as its factorization.

1813080721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44221522.

The product of its (nonzero) digits is 2688, while the sum is 31.

The square root of 1813080721 is about 42580.2855908694. The cubic root of 1813080721 is about 1219.3799413393.

The spelling of 1813080721 in words is "one billion, eight hundred thirteen million, eighty thousand, seven hundred twenty-one".