21131331 has 16 divisors (see below), whose sum is σ = 30799104. Its totient is φ = 12808224.

The previous prime is 21131317. The next prime is 21131333. The reversal of 21131331 is 13313112.

It is not a de Polignac number, because 21131331 - 2⁹ = 21130819 is a prime.

It is a super-2 number, since 2×21131331² = 893066299663122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21131331.

It is not an unprimeable number, because it can be changed into a prime (21131333) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1431 + ... + 6656.

It is an arithmetic number, because the mean of its divisors is an integer number (1924944).

Almost surely, 2^21131331 is an apocalyptic number.

21131331 is a deficient number, since it is larger than the sum of its proper divisors (9667773).

21131331 is a wasteful number, since it uses less digits than its factorization.

21131331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8170.

The product of its digits is 54, while the sum is 15.

The square root of 21131331 is about 4596.8827481240. The cubic root of 21131331 is about 276.4663534471.

Adding to 21131331 its reverse (13313112), we get a palindrome (34444443).

The spelling of 21131331 in words is "twenty-one million, one hundred thirty-one thousand, three hundred thirty-one".