9815921 has 4 divisors (see below), whose sum is σ = 9828672. Its totient is φ = 9803172.

The previous prime is 9815909. The next prime is 9815941. The reversal of 9815921 is 1295189.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1295189 = 7 ⋅185027.

It is a cyclic number.

It is not a de Polignac number, because 9815921 - 2²² = 5621617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (9815941) by changing a digit.

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

It is an upside-down number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5141 + ... + 6786.

It is an arithmetic number, because the mean of its divisors is an integer number (2457168).

Almost surely, 2^9815921 is an apocalyptic number.

It is an amenable number.

9815921 is a deficient number, since it is larger than the sum of its proper divisors (12751).

9815921 is a wasteful number, since it uses less digits than its factorization.

9815921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12750.

The product of its digits is 6480, while the sum is 35.

The square root of 9815921 is about 3133.0370249967. The cubic root of 9815921 is about 214.1133196088.

The spelling of 9815921 in words is "nine million, eight hundred fifteen thousand, nine hundred twenty-one".