7931921 has 2 divisors, whose sum is σ = 7931922. Its totient is φ = 7931920.

The previous prime is 7931893. The next prime is 7931923. The reversal of 7931921 is 1291397.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6431296 + 1500625 = 2536^2 + 1225^2 .

It is a cyclic number.

It is not a de Polignac number, because 7931921 - 2⁶ = 7931857 is a prime.

Together with 7931923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (7931923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3965960 + 3965961.

It is an arithmetic number, because the mean of its divisors is an integer number (3965961).

Almost surely, 2^7931921 is an apocalyptic number.

It is an amenable number.

7931921 is a deficient number, since it is larger than the sum of its proper divisors (1).

7931921 is an equidigital number, since it uses as much as digits as its factorization.

7931921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3402, while the sum is 32.

The square root of 7931921 is about 2816.3666309627. The cubic root of 7931921 is about 199.4310580600.

The spelling of 7931921 in words is "seven million, nine hundred thirty-one thousand, nine hundred twenty-one".