781840 has 40 divisors (see below), whose sum is σ = 1886040. Its totient is φ = 301056.

The previous prime is 781819. The next prime is 781853. The reversal of 781840 is 48187.

781840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 35344 + 746496 = 188^2 + 864^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×781840² = 1222547571200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 781799 and 781808.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2152 + ... + 2488.

It is an arithmetic number, because the mean of its divisors is an integer number (47151).

2⁷⁸¹⁸⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 781840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (943020).

781840 is an abundant number, since it is smaller than the sum of its proper divisors (1104200).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

781840 is a wasteful number, since it uses less digits than its factorization.

781840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 379 (or 373 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 781840 is about 884.2171678949. The cubic root of 781840 is about 92.1239664703.

The spelling of 781840 in words is "seven hundred eighty-one thousand, eight hundred forty".