2778640 has 40 divisors (see below), whose sum is σ = 6606720. Its totient is φ = 1086336.

The previous prime is 2778619. The next prime is 2778647. The reversal of 2778640 is 468772.

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 = 2778596 and 2778605.

It is not an unprimeable number, because it can be changed into a prime (2778647) 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, 3391 + ... + 4129.

It is an arithmetic number, because the mean of its divisors is an integer number (165168).

2^2778640 is an apocalyptic number.

2778640 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 2778640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3303360).

2778640 is an abundant number, since it is smaller than the sum of its proper divisors (3828080).

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

2778640 is a wasteful number, since it uses less digits than its factorization.

2778640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 799 (or 793 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 34.

The square root of 2778640 is about 1666.9253132639. The cubic root of 2778640 is about 140.5866539067.

The spelling of 2778640 in words is "two million, seven hundred seventy-eight thousand, six hundred forty".