21716305 has 16 divisors (see below), whose sum is σ = 28529424. Its totient is φ = 15770880.

The previous prime is 21716291. The next prime is 21716309. The reversal of 21716305 is 50361712.

It can be written as a sum of positive squares in 8 ways, for example, as 767376 + 20948929 = 876^2 + 4577^2 .

It is not a de Polignac number, because 21716305 - 2¹⁵ = 21683537 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21716305.

It is not an unprimeable number, because it can be changed into a prime (21716309) 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 in 15 ways as a sum of consecutive naturals, for example, 1227 + ... + 6703.

It is an arithmetic number, because the mean of its divisors is an integer number (1783089).

Almost surely, 2^21716305 is an apocalyptic number.

It is an amenable number.

21716305 is a deficient number, since it is larger than the sum of its proper divisors (6813119).

21716305 is a wasteful number, since it uses less digits than its factorization.

21716305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5556.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21716305 is about 4660.0756431629. The cubic root of 21716305 is about 278.9942873836.

The spelling of 21716305 in words is "twenty-one million, seven hundred sixteen thousand, three hundred five".