20551565 has 4 divisors (see below), whose sum is σ = 24661884. Its totient is φ = 16441248.

The previous prime is 20551561. The next prime is 20551577. The reversal of 20551565 is 56515502.

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 10426441 + 10125124 = 3229^2 + 3182^2 .

It is a cyclic number.

It is not a de Polignac number, because 20551565 - 2² = 20551561 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20551561) 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, 2055152 + ... + 2055161.

It is an arithmetic number, because the mean of its divisors is an integer number (6165471).

Almost surely, 2^20551565 is an apocalyptic number.

It is an amenable number.

20551565 is a deficient number, since it is larger than the sum of its proper divisors (4110319).

20551565 is an equidigital number, since it uses as much as digits as its factorization.

20551565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4110318.

The product of its (nonzero) digits is 7500, while the sum is 29.

The square root of 20551565 is about 4533.3833943314. The cubic root of 20551565 is about 273.9144643943.

The spelling of 20551565 in words is "twenty million, five hundred fifty-one thousand, five hundred sixty-five".