21553331 has 16 divisors (see below), whose sum is σ = 23677920. Its totient is φ = 19605760.

The previous prime is 21553319. The next prime is 21553361. The reversal of 21553331 is 13335512.

It is a de Polignac number, because none of the positive numbers 2^k-21553331 is a prime.

It is a super-2 number, since 2×21553331² = 929092154391122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21553297 and 21553306.

It is not an unprimeable number, because it can be changed into a prime (21553361) 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, 201380 + ... + 201486.

It is an arithmetic number, because the mean of its divisors is an integer number (1479870).

Almost surely, 2^21553331 is an apocalyptic number.

21553331 is a deficient number, since it is larger than the sum of its proper divisors (2124589).

21553331 is an equidigital number, since it uses as much as digits as its factorization.

21553331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199 (or 165 counting only the distinct ones).

The product of its digits is 1350, while the sum is 23.

The square root of 21553331 is about 4642.5565155418. The cubic root of 21553331 is about 278.2946128821.

Adding to 21553331 its reverse (13335512), we get a palindrome (34888843).

The spelling of 21553331 in words is "twenty-one million, five hundred fifty-three thousand, three hundred thirty-one".