9721820 has 12 divisors (see below), whose sum is σ = 20415864. Its totient is φ = 3888720.

The previous prime is 9721813. The next prime is 9721823. The reversal of 9721820 is 281279.

It is a happy number.

It is a super-2 number, since 2×9721820² = 189027568224800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9721823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 243026 + ... + 243065.

It is an arithmetic number, because the mean of its divisors is an integer number (1701322).

Almost surely, 2^9721820 is an apocalyptic number.

It is an amenable number.

9721820 is an abundant number, since it is smaller than the sum of its proper divisors (10694044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9721820 is a wasteful number, since it uses less digits than its factorization.

9721820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 486100 (or 486098 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 9721820 is about 3117.9833225981. The cubic root of 9721820 is about 213.4269174912.

The spelling of 9721820 in words is "nine million, seven hundred twenty-one thousand, eight hundred twenty".