1605500561 has 4 divisors (see below), whose sum is σ = 1834857792. Its totient is φ = 1376143332.

The previous prime is 1605500557. The next prime is 1605500563. The reversal of 1605500561 is 1650055061.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1605500561 - 2² = 1605500557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1605500563) 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, 114678605 + ... + 114678618.

It is an arithmetic number, because the mean of its divisors is an integer number (458714448).

Almost surely, 2^1605500561 is an apocalyptic number.

It is an amenable number.

1605500561 is a deficient number, since it is larger than the sum of its proper divisors (229357231).

1605500561 is an equidigital number, since it uses as much as digits as its factorization.

1605500561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 229357230.

The product of its (nonzero) digits is 4500, while the sum is 29.

The square root of 1605500561 is about 40068.6980197760. The cubic root of 1605500561 is about 1170.9458737762.

It can be divided in two parts, 1605500 and 561, that added together give a palindrome (1606061).

The spelling of 1605500561 in words is "one billion, six hundred five million, five hundred thousand, five hundred sixty-one".