21755243 has 2 divisors, whose sum is σ = 21755244. Its totient is φ = 21755242.

The previous prime is 21755221. The next prime is 21755267. The reversal of 21755243 is 34255712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21755243 is a prime.

It is a Chen prime.

It is equal to p_1374725 and since 21755243 and 1374725 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21755143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10877621 + 10877622.

It is an arithmetic number, because the mean of its divisors is an integer number (10877622).

Almost surely, 2^21755243 is an apocalyptic number.

21755243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21755243 is an equidigital number, since it uses as much as digits as its factorization.

21755243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8400, while the sum is 29.

The square root of 21755243 is about 4664.2516012754. The cubic root of 21755243 is about 279.1609362552.

The spelling of 21755243 in words is "twenty-one million, seven hundred fifty-five thousand, two hundred forty-three".