21704191 has 2 divisors, whose sum is σ = 21704192. Its totient is φ = 21704190.

The previous prime is 21704171. The next prime is 21704197. The reversal of 21704191 is 19140712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21704191 - 2²³ = 13315583 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21704197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10852095 + 10852096.

It is an arithmetic number, because the mean of its divisors is an integer number (10852096).

Almost surely, 2^21704191 is an apocalyptic number.

21704191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21704191 is an equidigital number, since it uses as much as digits as its factorization.

21704191 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 25.

The square root of 21704191 is about 4658.7756975411. The cubic root of 21704191 is about 278.9424006341.

Subtracting from 21704191 its sum of digits (25), we obtain a triangular number (21704166 = T₆₅₈₈).

The spelling of 21704191 in words is "twenty-one million, seven hundred four thousand, one hundred ninety-one".