917921 has 4 divisors (see below), whose sum is σ = 939312. Its totient is φ = 896532.

The previous prime is 917893. The next prime is 917923. The reversal of 917921 is 129719.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-917921 is a prime.

It is a super-4 number, since 4×917921⁴ (a number of 25 digits) contains 4444 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 917921.

It is not an unprimeable number, because it can be changed into a prime (917923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10631 + ... + 10716.

It is an arithmetic number, because the mean of its divisors is an integer number (234828).

2⁹¹⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

917921 is a deficient number, since it is larger than the sum of its proper divisors (21391).

917921 is a wasteful number, since it uses less digits than its factorization.

917921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21390.

The product of its digits is 1134, while the sum is 29.

The square root of 917921 is about 958.0819380408. The cubic root of 917921 is about 97.1855660571.

The spelling of 917921 in words is "nine hundred seventeen thousand, nine hundred twenty-one".