2561621605 has 8 divisors (see below), whose sum is σ = 3173105664. Its totient is φ = 1983190800.

The previous prime is 2561621597. The next prime is 2561621609. The reversal of 2561621605 is 5061261652.

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

It is not a de Polignac number, because 2561621605 - 2³ = 2561621597 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 (2561621609) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8263141 + ... + 8263450.

It is an arithmetic number, because the mean of its divisors is an integer number (396638208).

Almost surely, 2^2561621605 is an apocalyptic number.

It is an amenable number.

2561621605 is a deficient number, since it is larger than the sum of its proper divisors (611484059).

2561621605 is a wasteful number, since it uses less digits than its factorization.

2561621605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16526627.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 2561621605 is about 50612.4649172514. The cubic root of 2561621605 is about 1368.2695407020.

The spelling of 2561621605 in words is "two billion, five hundred sixty-one million, six hundred twenty-one thousand, six hundred five".