2561605020 has 384 divisors, whose sum is σ = 9031680000. Its totient is φ = 598440960.

The previous prime is 2561605019. The next prime is 2561605021. The reversal of 2561605020 is 205061652.

2561605020 is a `hidden beast` number, since 2 + 56 + 1 + 605 + 0 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (2561605019) and next prime (2561605021).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561605021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 17191906 + ... + 17192054.

It is an arithmetic number, because the mean of its divisors is an integer number (23520000).

Almost surely, 2^2561605020 is an apocalyptic number.

2561605020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2561605020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4515840000).

2561605020 is an abundant number, since it is smaller than the sum of its proper divisors (6470074980).

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

2561605020 is a wasteful number, since it uses less digits than its factorization.

2561605020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290 (or 282 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 2561605020 is about 50612.3010739484. The cubic root of 2561605020 is about 1368.2665877809.

Adding to 2561605020 its reverse (205061652), we get a palindrome (2766666672).

The spelling of 2561605020 in words is "two billion, five hundred sixty-one million, six hundred five thousand, twenty".