6436656221 has 2 divisors, whose sum is σ = 6436656222. Its totient is φ = 6436656220.

The previous prime is 6436656217. The next prime is 6436656287. The reversal of 6436656221 is 1226566346.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6362455225 + 74200996 = 79765^2 + 8614^2 .

It is a cyclic number.

It is not a de Polignac number, because 6436656221 - 2² = 6436656217 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6436652221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3218328110 + 3218328111.

It is an arithmetic number, because the mean of its divisors is an integer number (3218328111).

Almost surely, 2^6436656221 is an apocalyptic number.

It is an amenable number.

6436656221 is a deficient number, since it is larger than the sum of its proper divisors (1).

6436656221 is an equidigital number, since it uses as much as digits as its factorization.

6436656221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 311040, while the sum is 41.

The square root of 6436656221 is about 80228.7742708313. The cubic root of 6436656221 is about 1860.1734355753.

The spelling of 6436656221 in words is "six billion, four hundred thirty-six million, six hundred fifty-six thousand, two hundred twenty-one".