645778513 has 8 divisors (see below), whose sum is σ = 665360936. Its totient is φ = 626486400.

The previous prime is 645778499. The next prime is 645778519. The reversal of 645778513 is 315877546.

It can be written as a sum of positive squares in 4 ways, for example, as 4068289 + 641710224 = 2017^2 + 25332^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 645778513 - 2¹⁷ = 645647441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645778519) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68058 + ... + 76963.

It is an arithmetic number, because the mean of its divisors is an integer number (83170117).

Almost surely, 2^645778513 is an apocalyptic number.

It is an amenable number.

645778513 is a deficient number, since it is larger than the sum of its proper divisors (19582423).

645778513 is a wasteful number, since it uses less digits than its factorization.

645778513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145155.

The product of its digits is 705600, while the sum is 46.

The square root of 645778513 is about 25412.1725360112. The cubic root of 645778513 is about 864.3597400456.

The spelling of 645778513 in words is "six hundred forty-five million, seven hundred seventy-eight thousand, five hundred thirteen".