21719171 has 4 divisors (see below), whose sum is σ = 22224312. Its totient is φ = 21214032.

The previous prime is 21719129. The next prime is 21719177. The reversal of 21719171 is 17191712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21719171 - 2¹⁸ = 21457027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21719177) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 252506 + ... + 252591.

It is an arithmetic number, because the mean of its divisors is an integer number (5556078).

Almost surely, 2^21719171 is an apocalyptic number.

21719171 is a deficient number, since it is larger than the sum of its proper divisors (505141).

21719171 is an equidigital number, since it uses as much as digits as its factorization.

21719171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505140.

The product of its digits is 882, while the sum is 29.

The square root of 21719171 is about 4660.3831387559. The cubic root of 21719171 is about 279.0065602274.

The spelling of 21719171 in words is "twenty-one million, seven hundred nineteen thousand, one hundred seventy-one".