21304991 has 2 divisors, whose sum is σ = 21304992. Its totient is φ = 21304990.

The previous prime is 21304979. The next prime is 21305003. The reversal of 21304991 is 19940312.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21304979) and next prime (21305003).

It is a cyclic number.

It is not a de Polignac number, because 21304991 - 2¹⁰ = 21303967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21304931) 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, 10652495 + 10652496.

It is an arithmetic number, because the mean of its divisors is an integer number (10652496).

Almost surely, 2^21304991 is an apocalyptic number.

21304991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21304991 is an equidigital number, since it uses as much as digits as its factorization.

21304991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21304991 is about 4615.7329862114. The cubic root of 21304991 is about 277.2216335814.

The spelling of 21304991 in words is "twenty-one million, three hundred four thousand, nine hundred ninety-one".