9865220821 has 4 divisors (see below), whose sum is σ = 9865474272. Its totient is φ = 9864967372.

The previous prime is 9865220759. The next prime is 9865220837. The reversal of 9865220821 is 1280225689.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 9865220821 - 2²³ = 9856832213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9865220851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 54691 + ... + 150736.

It is an arithmetic number, because the mean of its divisors is an integer number (2466368568).

Almost surely, 2^9865220821 is an apocalyptic number.

It is an amenable number.

9865220821 is a deficient number, since it is larger than the sum of its proper divisors (253451).

9865220821 is a wasteful number, since it uses less digits than its factorization.

9865220821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253450.

The product of its (nonzero) digits is 138240, while the sum is 43.

The square root of 9865220821 is about 99323.8179944770. The cubic root of 9865220821 is about 2144.7117788217.

The spelling of 9865220821 in words is "nine billion, eight hundred sixty-five million, two hundred twenty thousand, eight hundred twenty-one".