9867857821 has 16 divisors (see below), whose sum is σ = 10186705648. Its totient is φ = 9555148800.

The previous prime is 9867857809. The next prime is 9867857833. The reversal of 9867857821 is 1287587689.

It is an interprime number because it is at equal distance from previous prime (9867857809) and next prime (9867857833).

It can be written as a sum of positive squares in 8 ways, for example, as 4800411225 + 5067446596 = 69285^2 + 71186^2 .

It is a 10-Lehmer number, since φ(9867857821) divides (9867857821-1)¹⁰.

It is a cyclic number.

It is not a de Polignac number, because 9867857821 - 2¹¹ = 9867855773 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a self number, because there is not a number n which added to its sum of digits gives 9867857821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9867857861) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1137661 + ... + 1146301.

It is an arithmetic number, because the mean of its divisors is an integer number (636669103).

Almost surely, 2^9867857821 is an apocalyptic number.

It is an amenable number.

9867857821 is a deficient number, since it is larger than the sum of its proper divisors (318847827).

9867857821 is a wasteful number, since it uses less digits than its factorization.

9867857821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8992.

The product of its digits is 13547520, while the sum is 61.

The square root of 9867857821 is about 99337.0918690496. The cubic root of 9867857821 is about 2144.9028575354.

The spelling of 9867857821 in words is "nine billion, eight hundred sixty-seven million, eight hundred fifty-seven thousand, eight hundred twenty-one".