1813380781 has 4 divisors (see below), whose sum is σ = 1815623100. Its totient is φ = 1811138464.

The previous prime is 1813380757. The next prime is 1813380787. The reversal of 1813380781 is 1870833181.

It is a happy number.

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 893471881 + 919908900 = 29891^2 + 30330^2 .

It is a cyclic number.

It is not a de Polignac number, because 1813380781 - 2⁵ = 1813380749 is a prime.

It is a super-2 number, since 2×1813380781² = 6576699713800339922, which contains 22 as substring.

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 a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1813380787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1119946 + ... + 1121563.

It is an arithmetic number, because the mean of its divisors is an integer number (453905775).

Almost surely, 2^1813380781 is an apocalyptic number.

It is an amenable number.

1813380781 is a deficient number, since it is larger than the sum of its proper divisors (2242319).

1813380781 is an equidigital number, since it uses as much as digits as its factorization.

1813380781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2242318.

The product of its (nonzero) digits is 32256, while the sum is 40.

The square root of 1813380781 is about 42583.8089066725. The cubic root of 1813380781 is about 1219.4472056661.

The spelling of 1813380781 in words is "one billion, eight hundred thirteen million, three hundred eighty thousand, seven hundred eighty-one".