1281640 has 24 divisors (see below), whose sum is σ = 2899890. Its totient is φ = 509792.

The previous prime is 1281587. The next prime is 1281649. The reversal of 1281640 is 461821.

It can be written as a sum of positive squares in only one way, i.e., 1153476 + 128164 = 1074^2 + 358^2 .

It is not an unprimeable number, because it can be changed into a prime (1281649) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 7071 + ... + 7249.

2^1281640 is an apocalyptic number.

1281640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1281640 is an abundant number, since it is smaller than the sum of its proper divisors (1618250).

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

1281640 is an equidigital number, since it uses as much as digits as its factorization.

1281640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 369 (or 186 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 1281640 is about 1132.0954023403. The cubic root of 1281640 is about 108.6230561744.

It can be divided in two parts, 1281 and 640, that multiplied together give a triangular number (819840 = T₁₂₈₀).

The spelling of 1281640 in words is "one million, two hundred eighty-one thousand, six hundred forty".