6521661256 has 64 divisors (see below), whose sum is σ = 13539052800. Its totient is φ = 2920315200.

The previous prime is 6521661253. The next prime is 6521661271.

6521661256 is nontrivially palindromic in base 10.

It is a super-2 number, since 2×6521661256² = 85064131076022995072, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (6521661253) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3059311 + ... + 3061441.

It is an arithmetic number, because the mean of its divisors is an integer number (211547700).

Almost surely, 2^6521661256 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 6521661256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (6769526400).

6521661256 is an abundant number, since it is smaller than the sum of its proper divisors (7017391544).

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

6521661256 is a wasteful number, since it uses less digits than its factorization.

6521661256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2650 (or 2646 counting only the distinct ones).

The product of its digits is 129600, while the sum is 40.

The square root of 6521661256 is about 80756.8031561428. The cubic root of 6521661256 is about 1868.3263792733.

The spelling of 6521661256 in words is "six billion, five hundred twenty-one million, six hundred sixty-one thousand, two hundred fifty-six".