781904 has 10 divisors (see below), whose sum is σ = 1514970. Its totient is φ = 390944.

The previous prime is 781897. The next prime is 781919. The reversal of 781904 is 409187.

It can be written as a sum of positive squares in only one way, i.e., 577600 + 204304 = 760^2 + 452^2 .

It is a super-2 number, since 2×781904² = 1222747730432, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

781904 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 24419 + ... + 24450.

It is an arithmetic number, because the mean of its divisors is an integer number (151497).

2⁷⁸¹⁹⁰⁴ is an apocalyptic number.

It is an amenable number.

781904 is a deficient number, since it is larger than the sum of its proper divisors (733066).

781904 is a wasteful number, since it uses less digits than its factorization.

781904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48877 (or 48871 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 781904 is about 884.2533573586. The cubic root of 781904 is about 92.1264801018.

Subtracting from 781904 its sum of digits (29), we obtain a triangular number (781875 = T₁₂₅₀).

The spelling of 781904 in words is "seven hundred eighty-one thousand, nine hundred four".