20505553 has 4 divisors (see below), whose sum is σ = 21711780. Its totient is φ = 19299328.

The previous prime is 20505497. The next prime is 20505571. The reversal of 20505553 is 35550502.

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 14493249 + 6012304 = 3807^2 + 2452^2 .

It is a cyclic number.

It is not a de Polignac number, because 20505553 - 2⁹ = 20505041 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20505593) 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 3 ways as a sum of consecutive naturals, for example, 603088 + ... + 603121.

It is an arithmetic number, because the mean of its divisors is an integer number (5427945).

Almost surely, 2^20505553 is an apocalyptic number.

It is an amenable number.

20505553 is a deficient number, since it is larger than the sum of its proper divisors (1206227).

20505553 is a wasteful number, since it uses less digits than its factorization.

20505553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1206226.

The product of its (nonzero) digits is 3750, while the sum is 25.

The square root of 20505553 is about 4528.3057538112. The cubic root of 20505553 is about 273.7098932785.

The spelling of 20505553 in words is "twenty million, five hundred five thousand, five hundred fifty-three".