221520491 has 2 divisors, whose sum is σ = 221520492. Its totient is φ = 221520490.

The previous prime is 221520461. The next prime is 221520511. The reversal of 221520491 is 194025122.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 221520491 - 2⁶ = 221520427 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221520491.

It is not a weakly prime, because it can be changed into another prime (221520461) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110760245 + 110760246.

It is an arithmetic number, because the mean of its divisors is an integer number (110760246).

Almost surely, 2^221520491 is an apocalyptic number.

221520491 is a deficient number, since it is larger than the sum of its proper divisors (1).

221520491 is an equidigital number, since it uses as much as digits as its factorization.

221520491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 221520491 is about 14883.5644588250. The cubic root of 221520491 is about 605.0686268713.

The spelling of 221520491 in words is "two hundred twenty-one million, five hundred twenty thousand, four hundred ninety-one".