20139565 has 4 divisors (see below), whose sum is σ = 24167484. Its totient is φ = 16111648.

The previous prime is 20139557. The next prime is 20139583. The reversal of 20139565 is 56593102.

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 12752041 + 7387524 = 3571^2 + 2718^2 .

It is a cyclic number.

It is not a de Polignac number, because 20139565 - 2³ = 20139557 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 an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 2013952 + ... + 2013961.

It is an arithmetic number, because the mean of its divisors is an integer number (6041871).

Almost surely, 2^20139565 is an apocalyptic number.

It is an amenable number.

20139565 is a deficient number, since it is larger than the sum of its proper divisors (4027919).

20139565 is an equidigital number, since it uses as much as digits as its factorization.

20139565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4027918.

The product of its (nonzero) digits is 8100, while the sum is 31.

The square root of 20139565 is about 4487.7126690554. The cubic root of 20139565 is about 272.0716948046.

The spelling of 20139565 in words is "twenty million, one hundred thirty-nine thousand, five hundred sixty-five".