21253943 has 2 divisors, whose sum is σ = 21253944. Its totient is φ = 21253942.

The previous prime is 21253937. The next prime is 21253957. The reversal of 21253943 is 34935212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21253943 - 2¹⁰ = 21252919 is a prime.

It is equal to p_1344953 and since 21253943 and 1344953 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 (21253963) 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, 10626971 + 10626972.

It is an arithmetic number, because the mean of its divisors is an integer number (10626972).

Almost surely, 2^21253943 is an apocalyptic number.

21253943 is a deficient number, since it is larger than the sum of its proper divisors (1).

21253943 is an equidigital number, since it uses as much as digits as its factorization.

21253943 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 29.

The square root of 21253943 is about 4610.1998872066. The cubic root of 21253943 is about 277.0000434429. Note that the first 4 decimals are identical.

The spelling of 21253943 in words is "twenty-one million, two hundred fifty-three thousand, nine hundred forty-three".