2781540 has 120 divisors (see below), whose sum is σ = 9330552. Its totient is φ = 691200.

The previous prime is 2781521. The next prime is 2781577. The reversal of 2781540 is 451872.

It can be written as a sum of positive squares in 4 ways, for example, as 1327104 + 1454436 = 1152^2 + 1206^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 27490 + ... + 27590.

2^2781540 is an apocalyptic number.

2781540 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 2781540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4665276).

2781540 is an abundant number, since it is smaller than the sum of its proper divisors (6549012).

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

2781540 is a wasteful number, since it uses less digits than its factorization.

2781540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139 (or 128 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 2781540 is about 1667.7949514254. The cubic root of 2781540 is about 140.6355458758.

It can be divided in two parts, 2781 and 540, that added together give a triangular number (3321 = T₈₁).

The spelling of 2781540 in words is "two million, seven hundred eighty-one thousand, five hundred forty".