646465612561 has 4 divisors (see below), whose sum is σ = 646468721892. Its totient is φ = 646462503232.

The previous prime is 646465612549. The next prime is 646465612577. The reversal of 646465612561 is 165216564646.

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 535576612561 + 110889000000 = 731831^2 + 333000^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646465612561 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 646465612499 and 646465612508.

It is not an unprimeable number, because it can be changed into a prime (646465612531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1218580 + ... + 1666693.

It is an arithmetic number, because the mean of its divisors is an integer number (161617180473).

Almost surely, 2^646465612561 is an apocalyptic number.

It is an amenable number.

646465612561 is a deficient number, since it is larger than the sum of its proper divisors (3109331).

646465612561 is a wasteful number, since it uses less digits than its factorization.

646465612561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3109330.

The product of its digits is 6220800, while the sum is 52.

The spelling of 646465612561 in words is "six hundred forty-six billion, four hundred sixty-five million, six hundred twelve thousand, five hundred sixty-one".