218525581 has 2 divisors, whose sum is σ = 218525582. Its totient is φ = 218525580.

The previous prime is 218525579. The next prime is 218525591. The reversal of 218525581 is 185525812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 192932100 + 25593481 = 13890^2 + 5059^2 .

It is a cyclic number.

It is not a de Polignac number, because 218525581 - 2¹ = 218525579 is a prime.

It is a super-2 number, since 2×218525581² = 95506859102775122, which contains 22 as substring.

Together with 218525579, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 218525581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218525501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109262790 + 109262791.

It is an arithmetic number, because the mean of its divisors is an integer number (109262791).

Almost surely, 2^218525581 is an apocalyptic number.

It is an amenable number.

218525581 is a deficient number, since it is larger than the sum of its proper divisors (1).

218525581 is an equidigital number, since it uses as much as digits as its factorization.

218525581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32000, while the sum is 37.

The square root of 218525581 is about 14782.6107640024. The cubic root of 218525581 is about 602.3294453624.

The spelling of 218525581 in words is "two hundred eighteen million, five hundred twenty-five thousand, five hundred eighty-one".