851840 has 64 divisors (see below), whose sum is σ = 2239920. Its totient is φ = 309760.

The previous prime is 851839. The next prime is 851843. The reversal of 851840 is 48158.

It is a tau number, because it is divible by the number of its divisors (64).

It is a nialpdrome in base 11.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (851843) 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 7 ways as a sum of consecutive naturals, for example, 77435 + ... + 77445.

2⁸⁵¹⁸⁴⁰ is an apocalyptic number.

851840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 851840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1119960).

851840 is an abundant number, since it is smaller than the sum of its proper divisors (1388080).

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

851840 is an equidigital number, since it uses as much as digits as its factorization.

851840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52 (or 18 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 26.

The square root of 851840 is about 922.9517863897. The cubic root of 851840 is about 94.7951263614.

Multiplying 851840 by its sum of digits (26), we get a triangular number (22147840 = T₆₆₅₅).

Adding to 851840 its reverse (48158), we get a palindrome (899998).

It can be divided in two parts, 8518 and 40, that added together give a palindrome (8558).

The spelling of 851840 in words is "eight hundred fifty-one thousand, eight hundred forty".