9917921 has 4 divisors (see below), whose sum is σ = 10680852. Its totient is φ = 9154992.

The previous prime is 9917911. The next prime is 9917939. The reversal of 9917921 is 1297199.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1852321 + 8065600 = 1361^2 + 2840^2 .

It is a cyclic number.

It is not a de Polignac number, because 9917921 - 2¹⁸ = 9655777 is a prime.

It is not an unprimeable number, because it can be changed into a prime (9917911) 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, 381446 + ... + 381471.

It is an arithmetic number, because the mean of its divisors is an integer number (2670213).

Almost surely, 2^9917921 is an apocalyptic number.

It is an amenable number.

9917921 is a deficient number, since it is larger than the sum of its proper divisors (762931).

9917921 is a wasteful number, since it uses less digits than its factorization.

9917921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 762930.

The product of its digits is 10206, while the sum is 38.

The square root of 9917921 is about 3149.2730907306. The cubic root of 9917921 is about 214.8524027541.

The spelling of 9917921 in words is "nine million, nine hundred seventeen thousand, nine hundred twenty-one".