21033391 has 2 divisors, whose sum is σ = 21033392. Its totient is φ = 21033390.

The previous prime is 21033371. The next prime is 21033401. The reversal of 21033391 is 19333012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21033391 - 2⁷ = 21033263 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21033371) 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, 10516695 + 10516696.

It is an arithmetic number, because the mean of its divisors is an integer number (10516696).

Almost surely, 2^21033391 is an apocalyptic number.

21033391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21033391 is an equidigital number, since it uses as much as digits as its factorization.

21033391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 22.

The square root of 21033391 is about 4586.2175046546. The cubic root of 21033391 is about 276.0385675643.

The spelling of 21033391 in words is "twenty-one million, thirty-three thousand, three hundred ninety-one".