21155543 has 2 divisors, whose sum is σ = 21155544. Its totient is φ = 21155542.

The previous prime is 21155513. The next prime is 21155551. The reversal of 21155543 is 34555112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21155543 - 2⁸ = 21155287 is a prime.

It is a Chen prime.

It is equal to p_1339172 and since 21155543 and 1339172 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 (21155503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577771 + 10577772.

It is an arithmetic number, because the mean of its divisors is an integer number (10577772).

Almost surely, 2^21155543 is an apocalyptic number.

21155543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155543 is an equidigital number, since it uses as much as digits as its factorization.

21155543 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3000, while the sum is 26.

The square root of 21155543 is about 4599.5155179649. The cubic root of 21155543 is about 276.5719036436.

The spelling of 21155543 in words is "twenty-one million, one hundred fifty-five thousand, five hundred forty-three".