1781806013 has 4 divisors (see below), whose sum is σ = 1918868028. Its totient is φ = 1644744000.

The previous prime is 1781805979. The next prime is 1781806027. The reversal of 1781806013 is 3106081871.

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 510669604 + 1271136409 = 22598^2 + 35653^2 .

It is a cyclic number.

It is not a de Polignac number, because 1781806013 - 2²⁰ = 1780757437 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781806043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68530988 + ... + 68531013.

It is an arithmetic number, because the mean of its divisors is an integer number (479717007).

Almost surely, 2^1781806013 is an apocalyptic number.

1781806013 is a gapful number since it is divisible by the number (13) formed by its first and last digit.

It is an amenable number.

1781806013 is a deficient number, since it is larger than the sum of its proper divisors (137062015).

1781806013 is a wasteful number, since it uses less digits than its factorization.

1781806013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137062014.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 1781806013 is about 42211.4440999121. Note that the first 3 decimals coincide. The cubic root of 1781806013 is about 1212.3280119961.

Adding to 1781806013 its reverse (3106081871), we get a palindrome (4887887884).

The spelling of 1781806013 in words is "one billion, seven hundred eighty-one million, eight hundred six thousand, thirteen".