813781 has 4 divisors (see below), whose sum is σ = 840064. Its totient is φ = 787500.

The previous prime is 813767. The next prime is 813797. The reversal of 813781 is 187318.

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 813781 - 2⁵ = 813749 is a prime.

It is a super-2 number, since 2×813781² = 1324479031922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (813721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13095 + ... + 13156.

It is an arithmetic number, because the mean of its divisors is an integer number (210016).

2⁸¹³⁷⁸¹ is an apocalyptic number.

It is an amenable number.

813781 is a deficient number, since it is larger than the sum of its proper divisors (26283).

813781 is a wasteful number, since it uses less digits than its factorization.

813781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26282.

The product of its digits is 1344, while the sum is 28.

The square root of 813781 is about 902.0981099637. The cubic root of 813781 is about 93.3617926251.

The spelling of 813781 in words is "eight hundred thirteen thousand, seven hundred eighty-one".