221656997 has 2 divisors, whose sum is σ = 221656998. Its totient is φ = 221656996.

The previous prime is 221656993. The next prime is 221657039. The reversal of 221656997 is 799656122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 197852356 + 23804641 = 14066^2 + 4879^2 .

It is a cyclic number.

It is not a de Polignac number, because 221656997 - 2² = 221656993 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221656991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110828498 + 110828499.

It is an arithmetic number, because the mean of its divisors is an integer number (110828499).

Almost surely, 2^221656997 is an apocalyptic number.

It is an amenable number.

221656997 is a deficient number, since it is larger than the sum of its proper divisors (1).

221656997 is an equidigital number, since it uses as much as digits as its factorization.

221656997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 408240, while the sum is 47.

The square root of 221656997 is about 14888.1495492220. The cubic root of 221656997 is about 605.1928870660.

The spelling of 221656997 in words is "two hundred twenty-one million, six hundred fifty-six thousand, nine hundred ninety-seven".