7991921 has 16 divisors (see below), whose sum is σ = 9745920. Its totient is φ = 6397440.

The previous prime is 7991897. The next prime is 7991939. The reversal of 7991921 is 1291997.

It is not a de Polignac number, because 7991921 - 2⁶ = 7991857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7991941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28301 + ... + 28581.

It is an arithmetic number, because the mean of its divisors is an integer number (609120).

Almost surely, 2^7991921 is an apocalyptic number.

It is an amenable number.

7991921 is a deficient number, since it is larger than the sum of its proper divisors (1753999).

7991921 is a wasteful number, since it uses less digits than its factorization.

7991921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544.

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

The square root of 7991921 is about 2826.9985850722. The cubic root of 7991921 is about 199.9326523240.

The spelling of 7991921 in words is "seven million, nine hundred ninety-one thousand, nine hundred twenty-one".