2581661 has 4 divisors (see below), whose sum is σ = 2607324. Its totient is φ = 2556000.

The previous prime is 2581651. The next prime is 2581669. The reversal of 2581661 is 1661852.

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 2325625 + 256036 = 1525^2 + 506^2 .

It is a cyclic number.

It is not a de Polignac number, because 2581661 - 2⁶ = 2581597 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 (2581669) 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, 12680 + ... + 12881.

It is an arithmetic number, because the mean of its divisors is an integer number (651831).

2^2581661 is an apocalyptic number.

It is an amenable number.

2581661 is a deficient number, since it is larger than the sum of its proper divisors (25663).

2581661 is a wasteful number, since it uses less digits than its factorization.

2581661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25662.

The product of its digits is 2880, while the sum is 29.

The square root of 2581661 is about 1606.7548039449. The cubic root of 2581661 is about 137.1828237415.

The spelling of 2581661 in words is "two million, five hundred eighty-one thousand, six hundred sixty-one".