1285840 has 20 divisors (see below), whose sum is σ = 2989764. Its totient is φ = 514304.

The previous prime is 1285813. The next prime is 1285841. The reversal of 1285840 is 485821.

It can be written as a sum of positive squares in 2 ways, for example, as 341056 + 944784 = 584^2 + 972^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 1285799 and 1285808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1285841) 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, 7957 + ... + 8116.

2^1285840 is an apocalyptic number.

1285840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1285840 is an abundant number, since it is smaller than the sum of its proper divisors (1703924).

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

1285840 is a wasteful number, since it uses less digits than its factorization.

1285840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16086 (or 16080 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 28.

The square root of 1285840 is about 1133.9488524620. The cubic root of 1285840 is about 108.7415812393.

The spelling of 1285840 in words is "one million, two hundred eighty-five thousand, eight hundred forty".