9861221 has 2 divisors, whose sum is σ = 9861222. Its totient is φ = 9861220.

The previous prime is 9861217. The next prime is 9861223. The reversal of 9861221 is 1221689.

9861221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8008900 + 1852321 = 2830^2 + 1361^2 .

It is a cyclic number.

It is not a de Polignac number, because 9861221 - 2² = 9861217 is a prime.

It is a super-2 number, since 2×9861221² = 194487359221682, which contains 22 as substring.

Together with 9861223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9861223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4930610 + 4930611.

It is an arithmetic number, because the mean of its divisors is an integer number (4930611).

Almost surely, 2^9861221 is an apocalyptic number.

It is an amenable number.

9861221 is a deficient number, since it is larger than the sum of its proper divisors (1).

9861221 is an equidigital number, since it uses as much as digits as its factorization.

9861221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 9861221 is about 3140.2581104107. The cubic root of 9861221 is about 214.4421884218.

The spelling of 9861221 in words is "nine million, eight hundred sixty-one thousand, two hundred twenty-one".