221500021 has 8 divisors (see below), whose sum is σ = 235557720. Its totient is φ = 207556608.

The previous prime is 221499989. The next prime is 221500039. The reversal of 221500021 is 120005122.

It can be written as a sum of positive squares in 4 ways, for example, as 42315025 + 179184996 = 6505^2 + 13386^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 221500021 - 2⁵ = 221499989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221499974 and 221500010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221503021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24556 + ... + 32341.

It is an arithmetic number, because the mean of its divisors is an integer number (29444715).

Almost surely, 2^221500021 is an apocalyptic number.

It is an amenable number.

221500021 is a deficient number, since it is larger than the sum of its proper divisors (14057699).

221500021 is a wasteful number, since it uses less digits than its factorization.

221500021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57143.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 221500021 is about 14882.8767716460. The cubic root of 221500021 is about 605.0499888117.

Adding to 221500021 its reverse (120005122), we get a palindrome (341505143).

The spelling of 221500021 in words is "two hundred twenty-one million, five hundred thousand, twenty-one".