221690257 has 2 divisors, whose sum is σ = 221690258. Its totient is φ = 221690256.

The previous prime is 221690237. The next prime is 221690263. The reversal of 221690257 is 752096122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 180203776 + 41486481 = 13424^2 + 6441^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221690257 is a prime.

It is not a weakly prime, because it can be changed into another prime (221690237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110845128 + 110845129.

It is an arithmetic number, because the mean of its divisors is an integer number (110845129).

Almost surely, 2^221690257 is an apocalyptic number.

It is an amenable number.

221690257 is a deficient number, since it is larger than the sum of its proper divisors (1).

221690257 is an equidigital number, since it uses as much as digits as its factorization.

221690257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 221690257 is about 14889.2665030887. The cubic root of 221690257 is about 605.2231556175.

The spelling of 221690257 in words is "two hundred twenty-one million, six hundred ninety thousand, two hundred fifty-seven".