640444651 has 36 divisors (see below), whose sum is σ = 827238720. Its totient is φ = 493970400.

The previous prime is 640444631. The next prime is 640444661. The reversal of 640444651 is 156444046.

640444651 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640444651 - 2⁷ = 640444523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640444631) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 645766 + ... + 646756.

Almost surely, 2^640444651 is an apocalyptic number.

640444651 is a deficient number, since it is larger than the sum of its proper divisors (186794069).

640444651 is a wasteful number, since it uses less digits than its factorization.

640444651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1136 (or 1118 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 34.

The square root of 640444651 is about 25307.0079424653. The cubic root of 640444651 is about 861.9734072147.

Adding to 640444651 its reverse (156444046), we get a palindrome (796888697).

The spelling of 640444651 in words is "six hundred forty million, four hundred forty-four thousand, six hundred fifty-one".