865749956521 has 2 divisors, whose sum is σ = 865749956522. Its totient is φ = 865749956520.

The previous prime is 865749956507. The next prime is 865749956537. The reversal of 865749956521 is 125659947568.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 848865552921 + 16884403600 = 921339^2 + 129940^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-865749956521 is a prime.

It is a super-2 number, since 2×865749956521² (a number of 25 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (865749956551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432874978260 + 432874978261.

It is an arithmetic number, because the mean of its divisors is an integer number (432874978261).

Almost surely, 2^865749956521 is an apocalyptic number.

It is an amenable number.

865749956521 is a deficient number, since it is larger than the sum of its proper divisors (1).

865749956521 is an equidigital number, since it uses as much as digits as its factorization.

865749956521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 163296000, while the sum is 67.

The spelling of 865749956521 in words is "eight hundred sixty-five billion, seven hundred forty-nine million, nine hundred fifty-six thousand, five hundred twenty-one".