1608641561 has 4 divisors (see below), whose sum is σ = 1610596992. Its totient is φ = 1606686132.

The previous prime is 1608641539. The next prime is 1608641611. The reversal of 1608641561 is 1651468061.

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 a de Polignac number, because none of the positive numbers 2^k-1608641561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1608641161) 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, 976481 + ... + 978126.

It is an arithmetic number, because the mean of its divisors is an integer number (402649248).

Almost surely, 2^1608641561 is an apocalyptic number.

It is an amenable number.

1608641561 is a deficient number, since it is larger than the sum of its proper divisors (1955431).

1608641561 is an equidigital number, since it uses as much as digits as its factorization.

1608641561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1955430.

The product of its (nonzero) digits is 34560, while the sum is 38.

The square root of 1608641561 is about 40107.8740523603. The cubic root of 1608641561 is about 1171.7089888602.

The spelling of 1608641561 in words is "one billion, six hundred eight million, six hundred forty-one thousand, five hundred sixty-one".