647665985 has 4 divisors (see below), whose sum is σ = 777199188. Its totient is φ = 518132784.

The previous prime is 647665973. The next prime is 647666003. The reversal of 647665985 is 589566746.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 589566746 = 2 ⋅294783373.

It can be written as a sum of positive squares in 2 ways, for example, as 385258384 + 262407601 = 19628^2 + 16199^2 .

It is a cyclic number.

It is not a de Polignac number, because 647665985 - 2²⁰ = 646617409 is a prime.

It is a super-4 number, since 4×647665985⁴ (a number of 36 digits) contains 4444 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 647665985.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64766594 + ... + 64766603.

It is an arithmetic number, because the mean of its divisors is an integer number (194299797).

Almost surely, 2^647665985 is an apocalyptic number.

It is an amenable number.

647665985 is a deficient number, since it is larger than the sum of its proper divisors (129533203).

647665985 is a wasteful number, since it uses less digits than its factorization.

647665985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129533202.

The product of its digits is 10886400, while the sum is 56.

The square root of 647665985 is about 25449.2826028554. The cubic root of 647665985 is about 865.2010336090.

The spelling of 647665985 in words is "six hundred forty-seven million, six hundred sixty-five thousand, nine hundred eighty-five".