21124391 has 2 divisors, whose sum is σ = 21124392. Its totient is φ = 21124390.

The previous prime is 21124357. The next prime is 21124459. The reversal of 21124391 is 19342112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21124391 - 2¹⁴ = 21108007 is a prime.

It is a Chen prime.

It is equal to p_1337342 and since 21124391 and 1337342 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21124321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562195 + 10562196.

It is an arithmetic number, because the mean of its divisors is an integer number (10562196).

Almost surely, 2^21124391 is an apocalyptic number.

21124391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21124391 is an equidigital number, since it uses as much as digits as its factorization.

21124391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 432, while the sum is 23.

The square root of 21124391 is about 4596.1278267690. The cubic root of 21124391 is about 276.4360842293.

The spelling of 21124391 in words is "twenty-one million, one hundred twenty-four thousand, three hundred ninety-one".