21079391 has 2 divisors, whose sum is σ = 21079392. Its totient is φ = 21079390.

The previous prime is 21079369. The next prime is 21079393. The reversal of 21079391 is 19397012.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21079391 - 2⁶ = 21079327 is a prime.

Together with 21079393, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21079393) 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 as a sum of consecutive naturals, namely, 10539695 + 10539696.

It is an arithmetic number, because the mean of its divisors is an integer number (10539696).

Almost surely, 2^21079391 is an apocalyptic number.

21079391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21079391 is an equidigital number, since it uses as much as digits as its factorization.

21079391 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21079391 is about 4591.2297916789. The cubic root of 21079391 is about 276.2396530457.

The spelling of 21079391 in words is "twenty-one million, seventy-nine thousand, three hundred ninety-one".