6891221 has 2 divisors, whose sum is σ = 6891222. Its totient is φ = 6891220.

The previous prime is 6891217. The next prime is 6891251. The reversal of 6891221 is 1221986.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6100900 + 790321 = 2470^2 + 889^2 .

It is a cyclic number.

It is not a de Polignac number, because 6891221 - 2² = 6891217 is a prime.

It is a nialpdrome in base 14.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6891211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3445610 + 3445611.

It is an arithmetic number, because the mean of its divisors is an integer number (3445611).

Almost surely, 2^6891221 is an apocalyptic number.

It is an amenable number.

6891221 is a deficient number, since it is larger than the sum of its proper divisors (1).

6891221 is an equidigital number, since it uses as much as digits as its factorization.

6891221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 29.

The square root of 6891221 is about 2625.1135213548. The cubic root of 6891221 is about 190.2970514979.

The spelling of 6891221 in words is "six million, eight hundred ninety-one thousand, two hundred twenty-one".