220021981 has 2 divisors, whose sum is σ = 220021982. Its totient is φ = 220021980.

The previous prime is 220021897. The next prime is 220022009. The reversal of 220021981 is 189120022.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 115369081 + 104652900 = 10741^2 + 10230^2 .

It is a cyclic number.

It is not a de Polignac number, because 220021981 - 2⁹ = 220021469 is a prime.

It is a super-2 number, since 2×220021981² = 96819344246328722, which contains 22 as substring.

It is equal to p_12123691 and since 220021981 and 12123691 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (220027981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110010990 + 110010991.

It is an arithmetic number, because the mean of its divisors is an integer number (110010991).

Almost surely, 2^220021981 is an apocalyptic number.

It is an amenable number.

220021981 is a deficient number, since it is larger than the sum of its proper divisors (1).

220021981 is an equidigital number, since it uses as much as digits as its factorization.

220021981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 220021981 is about 14833.1379350426. The cubic root of 220021981 is about 603.7011783340.

The spelling of 220021981 in words is "two hundred twenty million, twenty-one thousand, nine hundred eighty-one".