6665626521 has 24 divisors (see below), whose sum is σ = 9802937664. Its totient is φ = 4363492320.

The previous prime is 6665626519. The next prime is 6665626549. The reversal of 6665626521 is 1256265666.

It is a happy number.

It is not a de Polignac number, because 6665626521 - 2¹ = 6665626519 is a prime.

It is not an unprimeable number, because it can be changed into a prime (6665626511) 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 23 ways as a sum of consecutive naturals, for example, 173716 + ... + 208586.

It is an arithmetic number, because the mean of its divisors is an integer number (408455736).

Almost surely, 2^6665626521 is an apocalyptic number.

It is an amenable number.

6665626521 is a deficient number, since it is larger than the sum of its proper divisors (3137311143).

6665626521 is a wasteful number, since it uses less digits than its factorization.

6665626521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35261 (or 35258 counting only the distinct ones).

The product of its digits is 777600, while the sum is 45.

The square root of 6665626521 is about 81643.2882789516. The cubic root of 6665626521 is about 1881.9741712163.

The spelling of 6665626521 in words is "six billion, six hundred sixty-five million, six hundred twenty-six thousand, five hundred twenty-one".