21126331 has 4 divisors (see below), whose sum is σ = 21141000. Its totient is φ = 21111664.

The previous prime is 21126317. The next prime is 21126337. The reversal of 21126331 is 13362112.

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 21126331 - 2¹⁵ = 21093563 is a prime.

It is a super-2 number, since 2×21126331² = 892643723043122, 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 = 21126299 and 21126308.

It is not an unprimeable number, because it can be changed into a prime (21126337) 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, 4906 + ... + 8143.

It is an arithmetic number, because the mean of its divisors is an integer number (5285250).

Almost surely, 2^21126331 is an apocalyptic number.

21126331 is a deficient number, since it is larger than the sum of its proper divisors (14669).

21126331 is a wasteful number, since it uses less digits than its factorization.

21126331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14668.

The product of its digits is 216, while the sum is 19.

The square root of 21126331 is about 4596.3388691436. The cubic root of 21126331 is about 276.4445463208. Note that the first 3 decimals are identical.

Adding to 21126331 its reverse (13362112), we get a palindrome (34488443).

The spelling of 21126331 in words is "twenty-one million, one hundred twenty-six thousand, three hundred thirty-one".