691064221 has 2 divisors, whose sum is σ = 691064222. Its totient is φ = 691064220.

The previous prime is 691064189. The next prime is 691064239. The reversal of 691064221 is 122460196.

691064221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 656076996 + 34987225 = 25614^2 + 5915^2 .

It is a cyclic number.

It is not a de Polignac number, because 691064221 - 2⁵ = 691064189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (691064261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345532110 + 345532111.

It is an arithmetic number, because the mean of its divisors is an integer number (345532111).

Almost surely, 2^691064221 is an apocalyptic number.

It is an amenable number.

691064221 is a deficient number, since it is larger than the sum of its proper divisors (1).

691064221 is an equidigital number, since it uses as much as digits as its factorization.

691064221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 691064221 is about 26288.1003687980. The cubic root of 691064221 is about 884.1096607304.

The spelling of 691064221 in words is "six hundred ninety-one million, sixty-four thousand, two hundred twenty-one".