21221331 has 8 divisors (see below), whose sum is σ = 28324800. Its totient is φ = 14132712.

The previous prime is 21221303. The next prime is 21221339. The reversal of 21221331 is 13312212.

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

It is not a de Polignac number, because 21221331 - 2⁹ = 21220819 is a prime.

It is a super-4 number, since 4×21221331⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 21221331.

It is not an unprimeable number, because it can be changed into a prime (21221339) 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, 220 + ... + 6518.

It is an arithmetic number, because the mean of its divisors is an integer number (3540600).

Almost surely, 2^21221331 is an apocalyptic number.

21221331 is a deficient number, since it is larger than the sum of its proper divisors (7103469).

21221331 is a wasteful number, since it uses less digits than its factorization.

21221331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7425.

The product of its digits is 72, while the sum is 15.

The square root of 21221331 is about 4606.6615894810. The cubic root of 21221331 is about 276.8582948476.

Adding to 21221331 its reverse (13312212), we get a palindrome (34533543).

The spelling of 21221331 in words is "twenty-one million, two hundred twenty-one thousand, three hundred thirty-one".