221765591 has 2 divisors, whose sum is σ = 221765592. Its totient is φ = 221765590.

The previous prime is 221765573. The next prime is 221765603. The reversal of 221765591 is 195567122.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 221765591 - 2²⁶ = 154656727 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 (221765501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110882795 + 110882796.

It is an arithmetic number, because the mean of its divisors is an integer number (110882796).

Almost surely, 2^221765591 is an apocalyptic number.

221765591 is a deficient number, since it is larger than the sum of its proper divisors (1).

221765591 is an equidigital number, since it uses as much as digits as its factorization.

221765591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 37800, while the sum is 38.

The square root of 221765591 is about 14891.7960971805. The cubic root of 221765591 is about 605.2917027852.

The spelling of 221765591 in words is "two hundred twenty-one million, seven hundred sixty-five thousand, five hundred ninety-one".