2178640 has 40 divisors (see below), whose sum is σ = 5131368. Its totient is φ = 860160.

The previous prime is 2178619. The next prime is 2178641. The reversal of 2178640 is 468712.

It can be written as a sum of positive squares in 4 ways, for example, as 35344 + 2143296 = 188^2 + 1464^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 2178599 and 2178608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2178641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8920 + ... + 9160.

2^2178640 is an apocalyptic number.

2178640 is a gapful number since it is divisible by the number (20) 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 2178640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2565684).

2178640 is an abundant number, since it is smaller than the sum of its proper divisors (2952728).

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

2178640 is a wasteful number, since it uses less digits than its factorization.

2178640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 367 (or 361 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 2178640 is about 1476.0216800576. The cubic root of 2178640 is about 129.6368563570.

The spelling of 2178640 in words is "two million, one hundred seventy-eight thousand, six hundred forty".