221331621 has 16 divisors (see below), whose sum is σ = 345112064. Its totient is φ = 123533424.

The previous prime is 221331611. The next prime is 221331623. The reversal of 221331621 is 126133122.

It is not a de Polignac number, because 221331621 - 2⁶ = 221331557 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221331623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 121651 + ... + 123456.

It is an arithmetic number, because the mean of its divisors is an integer number (21569504).

Almost surely, 2^221331621 is an apocalyptic number.

221331621 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

221331621 is a deficient number, since it is larger than the sum of its proper divisors (123780443).

221331621 is a wasteful number, since it uses less digits than its factorization.

221331621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245160.

The product of its digits is 432, while the sum is 21.

The square root of 221331621 is about 14877.2181875511. The cubic root of 221331621 is about 604.8966159888.

Adding to 221331621 its reverse (126133122), we get a palindrome (347464743).

The spelling of 221331621 in words is "two hundred twenty-one million, three hundred thirty-one thousand, six hundred twenty-one".