21240311 has 2 divisors, whose sum is σ = 21240312. Its totient is φ = 21240310.

The previous prime is 21240283. The next prime is 21240313. The reversal of 21240311 is 11304212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21240311 - 2¹⁴ = 21223927 is a prime.

It is a super-2 number, since 2×21240311² = 902301622753442, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21240313, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21240313) 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 as a sum of consecutive naturals, namely, 10620155 + 10620156.

It is an arithmetic number, because the mean of its divisors is an integer number (10620156).

Almost surely, 2^21240311 is an apocalyptic number.

21240311 is a deficient number, since it is larger than the sum of its proper divisors (1).

21240311 is an equidigital number, since it uses as much as digits as its factorization.

21240311 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21240311 is about 4608.7211892238. The cubic root of 21240311 is about 276.9408093801.

Adding to 21240311 its reverse (11304212), we get a palindrome (32544523).

The spelling of 21240311 in words is "twenty-one million, two hundred forty thousand, three hundred eleven".