645065681 has 8 divisors (see below), whose sum is σ = 702492840. Its totient is φ = 588753792.

The previous prime is 645065677. The next prime is 645065683. The reversal of 645065681 is 186560546.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1175056 + 643890625 = 1084^2 + 25375^2 .

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 645065681 - 2² = 645065677 is a prime.

It is a super-2 number, since 2×645065681² = 832219465607987522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645065683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 277610 + ... + 279923.

It is an arithmetic number, because the mean of its divisors is an integer number (87811605).

Almost surely, 2^645065681 is an apocalyptic number.

It is an amenable number.

645065681 is a deficient number, since it is larger than the sum of its proper divisors (57427159).

645065681 is a wasteful number, since it uses less digits than its factorization.

645065681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 557635.

The product of its (nonzero) digits is 172800, while the sum is 41.

The square root of 645065681 is about 25398.1432589077. The cubic root of 645065681 is about 864.0415865221.

The spelling of 645065681 in words is "six hundred forty-five million, sixty-five thousand, six hundred eighty-one".