221185655981 has 2 divisors, whose sum is σ = 221185655982. Its totient is φ = 221185655980.

The previous prime is 221185655969. The next prime is 221185656071. The reversal of 221185655981 is 189556581122.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 148590975625 + 72594680356 = 385475^2 + 269434^2 .

It is a cyclic number.

It is not a de Polignac number, because 221185655981 - 2⁶ = 221185655917 is a prime.

It is a super-2 number, since 2×221185655981² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221185654981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110592827990 + 110592827991.

It is an arithmetic number, because the mean of its divisors is an integer number (110592827991).

Almost surely, 2^221185655981 is an apocalyptic number.

It is an amenable number.

221185655981 is a deficient number, since it is larger than the sum of its proper divisors (1).

221185655981 is an equidigital number, since it uses as much as digits as its factorization.

221185655981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728000, while the sum is 53.

The spelling of 221185655981 in words is "two hundred twenty-one billion, one hundred eighty-five million, six hundred fifty-five thousand, nine hundred eighty-one".