20724565 has 4 divisors (see below), whose sum is σ = 24869484. Its totient is φ = 16579648.

The previous prime is 20724563. The next prime is 20724569. The reversal of 20724565 is 56542702.

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 10745284 + 9979281 = 3278^2 + 3159^2 .

It is a cyclic number.

It is not a de Polignac number, because 20724565 - 2¹ = 20724563 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20724563) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2072452 + ... + 2072461.

It is an arithmetic number, because the mean of its divisors is an integer number (6217371).

Almost surely, 2^20724565 is an apocalyptic number.

It is an amenable number.

20724565 is a deficient number, since it is larger than the sum of its proper divisors (4144919).

20724565 is an equidigital number, since it uses as much as digits as its factorization.

20724565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4144918.

The product of its (nonzero) digits is 16800, while the sum is 31.

The square root of 20724565 is about 4552.4240795427. The cubic root of 20724565 is about 274.6809081269.

The spelling of 20724565 in words is "twenty million, seven hundred twenty-four thousand, five hundred sixty-five".