6445640625 has 28 divisors (see below), whose sum is σ = 10742674992. Its totient is φ = 3437650000.

The previous prime is 6445640587. The next prime is 6445640629. The reversal of 6445640625 is 5260465446.

It is not a de Polignac number, because 6445640625 - 2⁶ = 6445640561 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (6445640629) by changing a digit.

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 27 ways as a sum of consecutive naturals, for example, 21879 + ... + 115628.

It is an arithmetic number, because the mean of its divisors is an integer number (383666964).

Almost surely, 2^6445640625 is an apocalyptic number.

It is an amenable number.

6445640625 is a deficient number, since it is larger than the sum of its proper divisors (4297034367).

6445640625 is an frugal number, since it uses more digits than its factorization.

6445640625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137540 (or 137515 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 42.

The square root of 6445640625 is about 80284.7471503772. The cubic root of 6445640625 is about 1861.0385213802.

The spelling of 6445640625 in words is "six billion, four hundred forty-five million, six hundred forty thousand, six hundred twenty-five".