2561640 has 32 divisors (see below), whose sum is σ = 7685280. Its totient is φ = 683072.

The previous prime is 2561633. The next prime is 2561651. The reversal of 2561640 is 461652.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 2561640.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10554 + ... + 10793.

It is an arithmetic number, because the mean of its divisors is an integer number (240165).

2^2561640 is an apocalyptic number.

2561640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2561640 is an abundant number, since it is smaller than the sum of its proper divisors (5123640).

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

2561640 is a wasteful number, since it uses less digits than its factorization.

2561640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21361 (or 21357 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 2561640 is about 1600.5124179462. The cubic root of 2561640 is about 136.8272815874.

The spelling of 2561640 in words is "two million, five hundred sixty-one thousand, six hundred forty".