21716805 has 16 divisors (see below), whose sum is σ = 37905984. Its totient is φ = 10529280.

The previous prime is 21716767. The next prime is 21716809. The reversal of 21716805 is 50861712.

It is not a de Polignac number, because 21716805 - 2¹⁸ = 21454661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716809) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 65644 + ... + 65973.

It is an arithmetic number, because the mean of its divisors is an integer number (2369124).

Almost surely, 2^21716805 is an apocalyptic number.

It is an amenable number.

21716805 is a deficient number, since it is larger than the sum of its proper divisors (16189179).

21716805 is a wasteful number, since it uses less digits than its factorization.

21716805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131636.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21716805 is about 4660.1292900519. The cubic root of 21716805 is about 278.9964285716.

The spelling of 21716805 in words is "twenty-one million, seven hundred sixteen thousand, eight hundred five".