6643666621 has 8 divisors (see below), whose sum is σ = 6786581760. Its totient is φ = 6501761952.

The previous prime is 6643666613. The next prime is 6643666649. The reversal of 6643666621 is 1266663466.

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 6643666621 - 2³ = 6643666613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6643666681) 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, 239320 + ... + 265633.

It is an arithmetic number, because the mean of its divisors is an integer number (848322720).

Almost surely, 2^6643666621 is an apocalyptic number.

It is an amenable number.

6643666621 is a deficient number, since it is larger than the sum of its proper divisors (142915139).

6643666621 is a wasteful number, since it uses less digits than its factorization.

6643666621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 505235.

The product of its digits is 1119744, while the sum is 46.

The square root of 6643666621 is about 81508.6904630420. The cubic root of 6643666621 is about 1879.9051767664.

The spelling of 6643666621 in words is "six billion, six hundred forty-three million, six hundred sixty-six thousand, six hundred twenty-one".