221687261 has 2 divisors, whose sum is σ = 221687262. Its totient is φ = 221687260.

The previous prime is 221687251. The next prime is 221687309. The reversal of 221687261 is 162786122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 174504100 + 47183161 = 13210^2 + 6869^2 .

It is a cyclic number.

It is not a de Polignac number, because 221687261 - 2⁶ = 221687197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221687251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110843630 + 110843631.

It is an arithmetic number, because the mean of its divisors is an integer number (110843631).

Almost surely, 2^221687261 is an apocalyptic number.

It is an amenable number.

221687261 is a deficient number, since it is larger than the sum of its proper divisors (1).

221687261 is an equidigital number, since it uses as much as digits as its factorization.

221687261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16128, while the sum is 35.

The square root of 221687261 is about 14889.1658933602. The cubic root of 221687261 is about 605.2204292058.

The spelling of 221687261 in words is "two hundred twenty-one million, six hundred eighty-seven thousand, two hundred sixty-one".