2557661 has 4 divisors (see below), whose sum is σ = 2564892. Its totient is φ = 2550432.

The previous prime is 2557649. The next prime is 2557663. The reversal of 2557661 is 1667552.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 498436 + 2059225 = 706^2 + 1435^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2557661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2557663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3056 + ... + 3801.

It is an arithmetic number, because the mean of its divisors is an integer number (641223).

2^2557661 is an apocalyptic number.

It is an amenable number.

2557661 is a deficient number, since it is larger than the sum of its proper divisors (7231).

2557661 is an equidigital number, since it uses as much as digits as its factorization.

2557661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7230.

The product of its digits is 12600, while the sum is 32.

The square root of 2557661 is about 1599.2688954644. The cubic root of 2557661 is about 136.7564001875.

The spelling of 2557661 in words is "two million, five hundred fifty-seven thousand, six hundred sixty-one".