6643616621 has 8 divisors (see below), whose sum is σ = 6838756344. Its totient is φ = 6451061760.

The previous prime is 6643616561. The next prime is 6643616647. The reversal of 6643616621 is 1266163466.

It can be written as a sum of positive squares in 4 ways, for example, as 1302199396 + 5341417225 = 36086^2 + 73085^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6643616621 - 2³⁰ = 5569874797 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6643610621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 641000 + ... + 651281.

It is an arithmetic number, because the mean of its divisors is an integer number (854844543).

Almost surely, 2^6643616621 is an apocalyptic number.

It is an amenable number.

6643616621 is a deficient number, since it is larger than the sum of its proper divisors (195139723).

6643616621 is a wasteful number, since it uses less digits than its factorization.

6643616621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1292431.

The product of its digits is 186624, while the sum is 41.

The square root of 6643616621 is about 81508.3837467042. The cubic root of 6643616621 is about 1879.9004607212.

The spelling of 6643616621 in words is "six billion, six hundred forty-three million, six hundred sixteen thousand, six hundred twenty-one".