21351331 has 4 divisors (see below), whose sum is σ = 21928432. Its totient is φ = 20774232.

The previous prime is 21351311. The next prime is 21351347. The reversal of 21351331 is 13315312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21351331 - 2¹³ = 21343139 is a prime.

It is a super-2 number, since 2×21351331² = 911758670943122, 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 = 21351299 and 21351308.

It is not an unprimeable number, because it can be changed into a prime (21351311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 288495 + ... + 288568.

It is an arithmetic number, because the mean of its divisors is an integer number (5482108).

Almost surely, 2^21351331 is an apocalyptic number.

21351331 is a deficient number, since it is larger than the sum of its proper divisors (577101).

21351331 is an equidigital number, since it uses as much as digits as its factorization.

21351331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577100.

The product of its digits is 270, while the sum is 19.

The square root of 21351331 is about 4620.7500473408. The cubic root of 21351331 is about 277.4224808497.

Adding to 21351331 its reverse (13315312), we get a palindrome (34666643).

The spelling of 21351331 in words is "twenty-one million, three hundred fifty-one thousand, three hundred thirty-one".