2561645 has 8 divisors (see below), whose sum is σ = 3254904. Its totient is φ = 1928704.

The previous prime is 2561633. The next prime is 2561651. The reversal of 2561645 is 5461652.

It can be written as a sum of positive squares in 4 ways, for example, as 121801 + 2439844 = 349^2 + 1562^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2561645 - 2⁸ = 2561389 is a prime.

It is a super-3 number, since 3×2561645³ = 50428736408170233375, which contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

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, 14984 + ... + 15153.

It is an arithmetic number, because the mean of its divisors is an integer number (406863).

2^2561645 is an apocalyptic number.

It is an amenable number.

2561645 is a deficient number, since it is larger than the sum of its proper divisors (693259).

2561645 is a wasteful number, since it uses less digits than its factorization.

2561645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30159.

The product of its digits is 7200, while the sum is 29.

The square root of 2561645 is about 1600.5139799452. The cubic root of 2561645 is about 136.8273706106.

The spelling of 2561645 in words is "two million, five hundred sixty-one thousand, six hundred forty-five".