6656621 has 2 divisors, whose sum is σ = 6656622. Its totient is φ = 6656620.

The previous prime is 6656603. The next prime is 6656623. The reversal of 6656621 is 1266566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4141225 + 2515396 = 2035^2 + 1586^2 .

It is a cyclic number.

It is not a de Polignac number, because 6656621 - 2¹⁸ = 6394477 is a prime.

Together with 6656623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6656623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3328310 + 3328311.

It is an arithmetic number, because the mean of its divisors is an integer number (3328311).

Almost surely, 2^6656621 is an apocalyptic number.

It is an amenable number.

6656621 is a deficient number, since it is larger than the sum of its proper divisors (1).

6656621 is an equidigital number, since it uses as much as digits as its factorization.

6656621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 32.

The square root of 6656621 is about 2580.0428291019. The cubic root of 6656621 is about 188.1126249112.

The spelling of 6656621 in words is "six million, six hundred fifty-six thousand, six hundred twenty-one".