1643667065 has 4 divisors (see below), whose sum is σ = 1972400484. Its totient is φ = 1314933648.

The previous prime is 1643667043. The next prime is 1643667071. The reversal of 1643667065 is 5607663461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5607663461 = 1607 ⋅3489523.

It can be written as a sum of positive squares in 2 ways, for example, as 515244601 + 1128422464 = 22699^2 + 33592^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643667065 - 2²² = 1639472761 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164366702 + ... + 164366711.

It is an arithmetic number, because the mean of its divisors is an integer number (493100121).

Almost surely, 2^1643667065 is an apocalyptic number.

It is an amenable number.

1643667065 is a deficient number, since it is larger than the sum of its proper divisors (328733419).

1643667065 is an equidigital number, since it uses as much as digits as its factorization.

1643667065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 328733418.

The product of its (nonzero) digits is 544320, while the sum is 44.

The square root of 1643667065 is about 40542.1640394294. The cubic root of 1643667065 is about 1180.1520116815.

The spelling of 1643667065 in words is "one billion, six hundred forty-three million, six hundred sixty-seven thousand, sixty-five".