645821650 has 12 divisors (see below), whose sum is σ = 1201228362. Its totient is φ = 258328640.

The previous prime is 645821641. The next prime is 645821651. The reversal of 645821650 is 56128546.

It can be written as a sum of positive squares in 3 ways, for example, as 298632961 + 347188689 = 17281^2 + 18633^2 .

It is not an unprimeable number, because it can be changed into a prime (645821651) 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 5 ways as a sum of consecutive naturals, for example, 6458167 + ... + 6458266.

Almost surely, 2^645821650 is an apocalyptic number.

645821650 is a deficient number, since it is larger than the sum of its proper divisors (555406712).

645821650 is a wasteful number, since it uses less digits than its factorization.

645821650 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12916445 (or 12916440 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 37.

The square root of 645821650 is about 25413.0212686331. The cubic root of 645821650 is about 864.3789855790.

The spelling of 645821650 in words is "six hundred forty-five million, eight hundred twenty-one thousand, six hundred fifty".