21543331 has 2 divisors, whose sum is σ = 21543332. Its totient is φ = 21543330.

The previous prime is 21543293. The next prime is 21543371. The reversal of 21543331 is 13334512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21543331 - 2¹⁹ = 21019043 is a prime.

It is a super-2 number, since 2×21543331² = 928230221151122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21543371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771665 + 10771666.

It is an arithmetic number, because the mean of its divisors is an integer number (10771666).

Almost surely, 2^21543331 is an apocalyptic number.

21543331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21543331 is an equidigital number, since it uses as much as digits as its factorization.

21543331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 22.

The square root of 21543331 is about 4641.4793977783. The cubic root of 21543331 is about 278.2515665329.

Adding to 21543331 its reverse (13334512), we get a palindrome (34877843).

The spelling of 21543331 in words is "twenty-one million, five hundred forty-three thousand, three hundred thirty-one".