1811113781 has 4 divisors (see below), whose sum is σ = 1823108064. Its totient is φ = 1799119500.

The previous prime is 1811113753. The next prime is 1811113823. The reversal of 1811113781 is 1873111181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1811113781 - 2²⁶ = 1744004917 is a prime.

It is a super-2 number, since 2×1811113781² = 6560266255456231922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1811113741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5996915 + ... + 5997216.

It is an arithmetic number, because the mean of its divisors is an integer number (455777016).

Almost surely, 2^1811113781 is an apocalyptic number.

It is an amenable number.

1811113781 is a deficient number, since it is larger than the sum of its proper divisors (11994283).

1811113781 is a wasteful number, since it uses less digits than its factorization.

1811113781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11994282.

The product of its digits is 1344, while the sum is 32.

The square root of 1811113781 is about 42557.1824842764. The cubic root of 1811113781 is about 1218.9388293314.

The spelling of 1811113781 in words is "one billion, eight hundred eleven million, one hundred thirteen thousand, seven hundred eighty-one".