7891921 has 4 divisors (see below), whose sum is σ = 8235072. Its totient is φ = 7548772.

The previous prime is 7891913. The next prime is 7891951. The reversal of 7891921 is 1291987.

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 not a de Polignac number, because 7891921 - 2³ = 7891913 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7891901) 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, 171541 + ... + 171586.

It is an arithmetic number, because the mean of its divisors is an integer number (2058768).

Almost surely, 2^7891921 is an apocalyptic number.

It is an amenable number.

7891921 is a deficient number, since it is larger than the sum of its proper divisors (343151).

7891921 is a wasteful number, since it uses less digits than its factorization.

7891921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343150.

The product of its digits is 9072, while the sum is 37.

The square root of 7891921 is about 2809.2563072813. The cubic root of 7891921 is about 199.0952550209.

The spelling of 7891921 in words is "seven million, eight hundred ninety-one thousand, nine hundred twenty-one".