21316705 has 4 divisors (see below), whose sum is σ = 25580052. Its totient is φ = 17053360.

The previous prime is 21316693. The next prime is 21316721. The reversal of 21316705 is 50761312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7656289 + 13660416 = 2767^2 + 3696^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21316705 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 21316705.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2131666 + ... + 2131675.

It is an arithmetic number, because the mean of its divisors is an integer number (6395013).

Almost surely, 2^21316705 is an apocalyptic number.

It is an amenable number.

21316705 is a deficient number, since it is larger than the sum of its proper divisors (4263347).

21316705 is an equidigital number, since it uses as much as digits as its factorization.

21316705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4263346.

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

The square root of 21316705 is about 4617.0017327266. The cubic root of 21316705 is about 277.2724319950.

It can be divided in two parts, 2131 and 6705, that added together give a square (8836 = 94²).

The spelling of 21316705 in words is "twenty-one million, three hundred sixteen thousand, seven hundred five".