8129921 has 2 divisors, whose sum is σ = 8129922. Its totient is φ = 8129920.

The previous prime is 8129917. The next prime is 8129923. The reversal of 8129921 is 1299218.

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., 8042896 + 87025 = 2836^2 + 295^2 .

It is a cyclic number.

It is not a de Polignac number, because 8129921 - 2² = 8129917 is a prime.

It is a Sophie Germain prime.

Together with 8129923, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (8129923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4064960 + 4064961.

It is an arithmetic number, because the mean of its divisors is an integer number (4064961).

Almost surely, 2^8129921 is an apocalyptic number.

It is an amenable number.

8129921 is a deficient number, since it is larger than the sum of its proper divisors (1).

8129921 is an equidigital number, since it uses as much as digits as its factorization.

8129921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 32.

The square root of 8129921 is about 2851.3016325882. The cubic root of 8129921 is about 201.0768663874.

The spelling of 8129921 in words is "eight million, one hundred twenty-nine thousand, nine hundred twenty-one".