781864 has 16 divisors (see below), whose sum is σ = 1552500. Its totient is φ = 367872.

The previous prime is 781861. The next prime is 781867. The reversal of 781864 is 468187.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (781861) and next prime (781867).

It can be written as a sum of positive squares in 2 ways, for example, as 756900 + 24964 = 870^2 + 158^2 .

It is a super-2 number, since 2×781864² = 1222622628992, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is not an unprimeable number, because it can be changed into a prime (781861) 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, 2739 + ... + 3010.

2⁷⁸¹⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

781864 is a deficient number, since it is larger than the sum of its proper divisors (770636).

781864 is a wasteful number, since it uses less digits than its factorization.

781864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5772 (or 5768 counting only the distinct ones).

The product of its digits is 10752, while the sum is 34.

The square root of 781864 is about 884.2307391173. The cubic root of 781864 is about 92.1249090982.

The spelling of 781864 in words is "seven hundred eighty-one thousand, eight hundred sixty-four".