6621557021 has 8 divisors (see below), whose sum is σ = 6714081984. Its totient is φ = 6529672800.

The previous prime is 6621556999. The next prime is 6621557023. The reversal of 6621557021 is 1207551266.

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 6621557021 - 2⁶ = 6621556957 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 (6621557023) 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 7 ways as a sum of consecutive naturals, for example, 139355 + ... + 180728.

It is an arithmetic number, because the mean of its divisors is an integer number (839260248).

Almost surely, 2^6621557021 is an apocalyptic number.

It is an amenable number.

6621557021 is a deficient number, since it is larger than the sum of its proper divisors (92524963).

6621557021 is a wasteful number, since it uses less digits than its factorization.

6621557021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320371.

The product of its (nonzero) digits is 25200, while the sum is 35.

The square root of 6621557021 is about 81372.9501800199. The cubic root of 6621557021 is about 1877.8174669473.

The spelling of 6621557021 in words is "six billion, six hundred twenty-one million, five hundred fifty-seven thousand, twenty-one".