645531685385 has 4 divisors (see below), whose sum is σ = 774638022468. Its totient is φ = 516425348304.

The previous prime is 645531685289. The next prime is 645531685387. The reversal of 645531685385 is 583586135546.

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 108465494281 + 537066191104 = 329341^2 + 732848^2 .

It is a cyclic number.

It is not a de Polignac number, because 645531685385 - 2³⁴ = 628351816201 is a prime.

It is a super-2 number, since 2×645531685385² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645531685387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64553168534 + ... + 64553168543.

It is an arithmetic number, because the mean of its divisors is an integer number (193659505617).

Almost surely, 2^645531685385 is an apocalyptic number.

It is an amenable number.

645531685385 is a deficient number, since it is larger than the sum of its proper divisors (129106337083).

645531685385 is a wasteful number, since it uses less digits than its factorization.

645531685385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129106337082.

The product of its digits is 51840000, while the sum is 59.

The spelling of 645531685385 in words is "six hundred forty-five billion, five hundred thirty-one million, six hundred eighty-five thousand, three hundred eighty-five".