1378665 has 12 divisors (see below), whose sum is σ = 2389764. Its totient is φ = 735264.

The previous prime is 1378639. The next prime is 1378669. The reversal of 1378665 is 5668731.

1378665 = T₇₀ + T₇₁ + ... + T₂₀₄.

It can be written as a sum of positive squares in 2 ways, for example, as 974169 + 404496 = 987^2 + 636^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1378665 is a prime.

1378665 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1378669) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15274 + ... + 15363.

It is an arithmetic number, because the mean of its divisors is an integer number (199147).

2^1378665 is an apocalyptic number.

1378665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1378665 is a deficient number, since it is larger than the sum of its proper divisors (1011099).

1378665 is a wasteful number, since it uses less digits than its factorization.

1378665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30648 (or 30645 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The square root of 1378665 is about 1174.1656612250. The cubic root of 1378665 is about 111.2977155078.

The spelling of 1378665 in words is "one million, three hundred seventy-eight thousand, six hundred sixty-five".