1281840 has 120 divisors (see below), whose sum is σ = 4664880. Its totient is φ = 290304.

The previous prime is 1281827. The next prime is 1281853. The reversal of 1281840 is 481821.

It is an interprime number because it is at equal distance from previous prime (1281827) and next prime (1281853).

It is a tau number, because it is divible by the number of its divisors (120).

It is a super-2 number, since 2×1281840² = 3286227571200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 1281840.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11706 + ... + 11814.

It is an arithmetic number, because the mean of its divisors is an integer number (38874).

2^1281840 is an apocalyptic number.

1281840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1281840 is the 654-th octagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1281840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2332440).

1281840 is an abundant number, since it is smaller than the sum of its proper divisors (3383040).

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

1281840 is a wasteful number, since it uses less digits than its factorization.

1281840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139 (or 126 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 24.

The square root of 1281840 is about 1132.1837306727. The cubic root of 1281840 is about 108.6287060921.

The spelling of 1281840 in words is "one million, two hundred eighty-one thousand, eight hundred forty".