221801021 has 16 divisors (see below), whose sum is σ = 248380608. Its totient is φ = 196732800.

The previous prime is 221800993. The next prime is 221801059. The reversal of 221801021 is 120108122.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 221801021 - 2¹⁰ = 221799997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221801071) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32606 + ... + 38816.

It is an arithmetic number, because the mean of its divisors is an integer number (15523788).

Almost surely, 2^221801021 is an apocalyptic number.

It is an amenable number.

221801021 is a deficient number, since it is larger than the sum of its proper divisors (26579587).

221801021 is a wasteful number, since it uses less digits than its factorization.

221801021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6332.

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 221801021 is about 14892.9856308263. The cubic root of 221801021 is about 605.3239355330.

Adding to 221801021 its reverse (120108122), we get a palindrome (341909143).

The spelling of 221801021 in words is "two hundred twenty-one million, eight hundred one thousand, twenty-one".