865647521 has 2 divisors, whose sum is σ = 865647522. Its totient is φ = 865647520.

The previous prime is 865647509. The next prime is 865647529. The reversal of 865647521 is 125746568.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 786241600 + 79405921 = 28040^2 + 8911^2 .

It is a cyclic number.

It is not a de Polignac number, because 865647521 - 2¹⁰ = 865646497 is a prime.

It is a super-2 number, since 2×865647521² = 1498691261226890882, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (865647529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 432823760 + 432823761.

It is an arithmetic number, because the mean of its divisors is an integer number (432823761).

Almost surely, 2^865647521 is an apocalyptic number.

It is an amenable number.

865647521 is a deficient number, since it is larger than the sum of its proper divisors (1).

865647521 is an equidigital number, since it uses as much as digits as its factorization.

865647521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 44.

The square root of 865647521 is about 29421.8884676018. Note that the first 3 decimals coincide. The cubic root of 865647521 is about 953.0456348872.

The spelling of 865647521 in words is "eight hundred sixty-five million, six hundred forty-seven thousand, five hundred twenty-one".