656221217 has 2 divisors, whose sum is σ = 656221218. Its totient is φ = 656221216.

The previous prime is 656221213. The next prime is 656221219. The reversal of 656221217 is 712122656.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 620209216 + 36012001 = 24904^2 + 6001^2 .

It is a cyclic number.

It is not a de Polignac number, because 656221217 - 2² = 656221213 is a prime.

It is a super-3 number, since 3×656221217³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 656221219, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (656221213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328110608 + 328110609.

It is an arithmetic number, because the mean of its divisors is an integer number (328110609).

Almost surely, 2^656221217 is an apocalyptic number.

It is an amenable number.

656221217 is a deficient number, since it is larger than the sum of its proper divisors (1).

656221217 is an equidigital number, since it uses as much as digits as its factorization.

656221217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10080, while the sum is 32.

The square root of 656221217 is about 25616.8151221029. The cubic root of 656221217 is about 868.9939562137.

The spelling of 656221217 in words is "six hundred fifty-six million, two hundred twenty-one thousand, two hundred seventeen".