6561521540 has 96 divisors (see below), whose sum is σ = 16229251584. Its totient is φ = 2181288960.

The previous prime is 6561521537. The next prime is 6561521557. The reversal of 6561521540 is 451251656.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 6561521540.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1608944 + ... + 1613016.

It is an arithmetic number, because the mean of its divisors is an integer number (169054704).

Almost surely, 2^6561521540 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6561521540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8114625792).

6561521540 is an abundant number, since it is smaller than the sum of its proper divisors (9667730044).

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

6561521540 is a wasteful number, since it uses less digits than its factorization.

6561521540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4437 (or 4435 counting only the distinct ones).

The product of its (nonzero) digits is 36000, while the sum is 35.

The square root of 6561521540 is about 81003.2193187407. The cubic root of 6561521540 is about 1872.1250437725.

The spelling of 6561521540 in words is "six billion, five hundred sixty-one million, five hundred twenty-one thousand, five hundred forty".