1639678465 has 4 divisors (see below), whose sum is σ = 1967614164. Its totient is φ = 1311742768.

The previous prime is 1639678463. The next prime is 1639678483. The reversal of 1639678465 is 5648769361.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5648769361 = 2441 ⋅2314121.

It can be written as a sum of positive squares in 2 ways, for example, as 209931121 + 1429747344 = 14489^2 + 37812^2 .

It is a cyclic number.

It is not a de Polignac number, because 1639678465 - 2¹ = 1639678463 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1639678463) 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, 163967842 + ... + 163967851.

It is an arithmetic number, because the mean of its divisors is an integer number (491903541).

Almost surely, 2^1639678465 is an apocalyptic number.

It is an amenable number.

1639678465 is a deficient number, since it is larger than the sum of its proper divisors (327935699).

1639678465 is an equidigital number, since it uses as much as digits as its factorization.

1639678465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 327935698.

The product of its digits is 6531840, while the sum is 55.

The square root of 1639678465 is about 40492.9433975847. The cubic root of 1639678465 is about 1179.1966343041.

The spelling of 1639678465 in words is "one billion, six hundred thirty-nine million, six hundred seventy-eight thousand, four hundred sixty-five".