21240743 has 2 divisors, whose sum is σ = 21240744. Its totient is φ = 21240742.

The previous prime is 21240719. The next prime is 21240761. The reversal of 21240743 is 34704212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21240743 - 2²⁰ = 20192167 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21240643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10620371 + 10620372.

It is an arithmetic number, because the mean of its divisors is an integer number (10620372).

Almost surely, 2^21240743 is an apocalyptic number.

21240743 is a deficient number, since it is larger than the sum of its proper divisors (1).

21240743 is an equidigital number, since it uses as much as digits as its factorization.

21240743 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21240743 is about 4608.7680566503. The cubic root of 21240743 is about 276.9426869047.

Adding to 21240743 its reverse (34704212), we get a palindrome (55944955).

The spelling of 21240743 in words is "twenty-one million, two hundred forty thousand, seven hundred forty-three".