9865545821 has 2 divisors, whose sum is σ = 9865545822. Its totient is φ = 9865545820.

The previous prime is 9865545817. The next prime is 9865545847. The reversal of 9865545821 is 1285455689.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6832840921 + 3032704900 = 82661^2 + 55070^2 .

It is a cyclic number.

It is not a de Polignac number, because 9865545821 - 2² = 9865545817 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9865545721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4932772910 + 4932772911.

It is an arithmetic number, because the mean of its divisors is an integer number (4932772911).

Almost surely, 2^9865545821 is an apocalyptic number.

It is an amenable number.

9865545821 is a deficient number, since it is larger than the sum of its proper divisors (1).

9865545821 is an equidigital number, since it uses as much as digits as its factorization.

9865545821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456000, while the sum is 53.

The square root of 9865545821 is about 99325.4540437646. The cubic root of 9865545821 is about 2144.7353303700.

The spelling of 9865545821 in words is "nine billion, eight hundred sixty-five million, five hundred forty-five thousand, eight hundred twenty-one".