6503565943681 has 3 divisors (see below), whose sum is σ = 6503568493891. Its totient is φ = 6503563393472.

The previous prime is 6503565943547. The next prime is 6503565943697. The reversal of 6503565943681 is 1863495653056.

The square root of 6503565943681 is 2550209.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 2934338166081 + 3569227777600 = 1712991^2 + 1889240^2 .

It is not a de Polignac number, because 6503565943681 - 2¹⁵ = 6503565910913 is a prime.

It is a super-2 number, since 2×6503565943681² (a number of 26 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6503565943781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1275105 + ... + 3825313.

Almost surely, 2^{6503565943681} is an apocalyptic number.

6503565943681 is the 2550209-th square number.

6503565943681 is the 1275105-th centered octagonal number.

It is an amenable number.

6503565943681 is a deficient number, since it is larger than the sum of its proper divisors (2550210).

6503565943681 is an frugal number, since it uses more digits than its factorization.

6503565943681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5100418 (or 2550209 counting only the distinct ones).

The product of its (nonzero) digits is 69984000, while the sum is 61.

The spelling of 6503565943681 in words is "six trillion, five hundred three billion, five hundred sixty-five million, nine hundred forty-three thousand, six hundred eighty-one".