1645644778 has 8 divisors (see below), whose sum is σ = 2613671172. Its totient is φ = 774421056.

The previous prime is 1645644773. The next prime is 1645644809. The reversal of 1645644778 is 8774465461.

It can be written as a sum of positive squares in 2 ways, for example, as 1579824009 + 65820769 = 39747^2 + 8113^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (1645644773) 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, 24200625 + ... + 24200692.

Almost surely, 2^1645644778 is an apocalyptic number.

1645644778 is a deficient number, since it is larger than the sum of its proper divisors (968026394).

1645644778 is a wasteful number, since it uses less digits than its factorization.

1645644778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48401336.

The product of its digits is 4515840, while the sum is 52.

The square root of 1645644778 is about 40566.5475237911. The cubic root of 1645644778 is about 1180.6251542326.

The spelling of 1645644778 in words is "one billion, six hundred forty-five million, six hundred forty-four thousand, seven hundred seventy-eight".