6621691 has 2 divisors, whose sum is σ = 6621692. Its totient is φ = 6621690.

The previous prime is 6621649. The next prime is 6621707. The reversal of 6621691 is 1961266.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 6621691 - 2¹¹ = 6619643 is a prime.

6621691 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (6621191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3310845 + 3310846.

It is an arithmetic number, because the mean of its divisors is an integer number (3310846).

Almost surely, 2^6621691 is an apocalyptic number.

6621691 is a deficient number, since it is larger than the sum of its proper divisors (1).

6621691 is an equidigital number, since it uses as much as digits as its factorization.

6621691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 31.

The square root of 6621691 is about 2573.2646579783. The cubic root of 6621691 is about 187.7830131965.

It can be divided in two parts, 66216 and 91, that multiplied together give a triangular number (6025656 = T₃₄₇₁).

The spelling of 6621691 in words is "six million, six hundred twenty-one thousand, six hundred ninety-one".