21306331 has 6 divisors (see below), whose sum is σ = 22016796. Its totient is φ = 20618100.

The previous prime is 21306317. The next prime is 21306343. The reversal of 21306331 is 13360312.

It is not a de Polignac number, because 21306331 - 2¹⁹ = 20782043 is a prime.

It is a super-2 number, since 2×21306331² = 907919481363122, 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 = 21306299 and 21306308.

It is not an unprimeable number, because it can be changed into a prime (21306301) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10125 + ... + 12046.

It is an arithmetic number, because the mean of its divisors is an integer number (3669466).

Almost surely, 2^21306331 is an apocalyptic number.

21306331 is a deficient number, since it is larger than the sum of its proper divisors (710465).

21306331 is an equidigital number, since it uses as much as digits as its factorization.

21306331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22233 (or 22202 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 19.

The square root of 21306331 is about 4615.8781396393. The cubic root of 21306331 is about 277.2274455090.

Adding to 21306331 its reverse (13360312), we get a palindrome (34666643).

The spelling of 21306331 in words is "twenty-one million, three hundred six thousand, three hundred thirty-one".