6640625 has 18 divisors (see below), whose sum is σ = 8789058. Its totient is φ = 5000000.

The previous prime is 6640597. The next prime is 6640631. The reversal of 6640625 is 5260466.

It can be written as a sum of positive squares in 9 ways, for example, as 3139984 + 3500641 = 1772^2 + 1871^2 .

It is not a de Polignac number, because 6640625 - 2⁸ = 6640369 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 5.

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 17 ways as a sum of consecutive naturals, for example, 390617 + ... + 390633.

It is an arithmetic number, because the mean of its divisors is an integer number (488281).

Almost surely, 2^6640625 is an apocalyptic number.

It is an amenable number.

6640625 is a deficient number, since it is larger than the sum of its proper divisors (2148433).

6640625 is an frugal number, since it uses more digits than its factorization.

6640625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57 (or 22 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 6640625 is about 2576.9410160110. The cubic root of 6640625 is about 187.9618245256.

The spelling of 6640625 in words is "six million, six hundred forty thousand, six hundred twenty-five".