221155661 has 2 divisors, whose sum is σ = 221155662. Its totient is φ = 221155660.

The previous prime is 221155639. The next prime is 221155673. The reversal of 221155661 is 166551122.

It is a happy number.

221155661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 196840900 + 24314761 = 14030^2 + 4931^2 .

It is a cyclic number.

It is not a de Polignac number, because 221155661 - 2²⁶ = 154046797 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 (221155631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110577830 + 110577831.

It is an arithmetic number, because the mean of its divisors is an integer number (110577831).

Almost surely, 2^221155661 is an apocalyptic number.

It is an amenable number.

221155661 is a deficient number, since it is larger than the sum of its proper divisors (1).

221155661 is an equidigital number, since it uses as much as digits as its factorization.

221155661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3600, while the sum is 29.

The square root of 221155661 is about 14871.3032717378. The cubic root of 221155661 is about 604.7362746471.

The spelling of 221155661 in words is "two hundred twenty-one million, one hundred fifty-five thousand, six hundred sixty-one".