221723981 has 4 divisors (see below), whose sum is σ = 222134364. Its totient is φ = 221313600.

The previous prime is 221723969. The next prime is 221723989. The reversal of 221723981 is 189327122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 89680900 + 132043081 = 9470^2 + 11491^2 .

It is a cyclic number.

It is not a de Polignac number, because 221723981 - 2⁶ = 221723917 is a prime.

It is a super-2 number, since 2×221723981² = 98323047500976722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221723989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 204380 + ... + 205461.

It is an arithmetic number, because the mean of its divisors is an integer number (55533591).

Almost surely, 2^221723981 is an apocalyptic number.

It is an amenable number.

221723981 is a deficient number, since it is larger than the sum of its proper divisors (410383).

221723981 is an equidigital number, since it uses as much as digits as its factorization.

221723981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 410382.

The product of its digits is 12096, while the sum is 35.

The square root of 221723981 is about 14890.3989536882. The cubic root of 221723981 is about 605.2538433454.

The spelling of 221723981 in words is "two hundred twenty-one million, seven hundred twenty-three thousand, nine hundred eighty-one".