820609505 has 4 divisors (see below), whose sum is σ = 984731412. Its totient is φ = 656487600.

The previous prime is 820609477. The next prime is 820609507. The reversal of 820609505 is 505906028.

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 211062784 + 609546721 = 14528^2 + 24689^2 .

It is not a de Polignac number, because 820609505 - 2²⁶ = 753500641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (820609507) 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, 82060946 + ... + 82060955.

It is an arithmetic number, because the mean of its divisors is an integer number (246182853).

Almost surely, 2^820609505 is an apocalyptic number.

It is an amenable number.

820609505 is a deficient number, since it is larger than the sum of its proper divisors (164121907).

820609505 is a wasteful number, since it uses less digits than its factorization.

820609505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164121906.

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 820609505 is about 28646.2825685987. The cubic root of 820609505 is about 936.2220116612. Note that the first 3 decimals are identical.

The spelling of 820609505 in words is "eight hundred twenty million, six hundred nine thousand, five hundred five".