6561361620 has 144 divisors (see below), whose sum is σ = 21923620992. Its totient is φ = 1575141120.

The previous prime is 6561361613. The next prime is 6561361661. The reversal of 6561361620 is 261631656.

6561361620 is a `hidden beast` number, since 6 + 5 + 6 + 13 + 616 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 187854 + ... + 220026.

It is an arithmetic number, because the mean of its divisors is an integer number (152247368).

Almost surely, 2^6561361620 is an apocalyptic number.

6561361620 is a gapful number since it is divisible by the number (60) 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 6561361620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (10961810496).

6561361620 is an abundant number, since it is smaller than the sum of its proper divisors (15362259372).

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

6561361620 is a wasteful number, since it uses less digits than its factorization.

6561361620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32302 (or 32297 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 36.

The square root of 6561361620 is about 81002.2321914649. The cubic root of 6561361620 is about 1872.1098342581.

It can be divided in two parts, 656136 and 1620, that added together give a palindrome (657756).

The spelling of 6561361620 in words is "six billion, five hundred sixty-one million, three hundred sixty-one thousand, six hundred twenty".