21493243 has 2 divisors, whose sum is σ = 21493244. Its totient is φ = 21493242.

The previous prime is 21493231. The next prime is 21493259. The reversal of 21493243 is 34239412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21493243 - 2¹⁷ = 21362171 is a prime.

It is not a weakly prime, because it can be changed into another prime (21493273) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746621 + 10746622.

It is an arithmetic number, because the mean of its divisors is an integer number (10746622).

Almost surely, 2^21493243 is an apocalyptic number.

21493243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493243 is an equidigital number, since it uses as much as digits as its factorization.

21493243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 28.

The square root of 21493243 is about 4636.0805644423. The cubic root of 21493243 is about 278.0357552824.

It can be divided in two parts, 21493 and 243, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21493243 in words is "twenty-one million, four hundred ninety-three thousand, two hundred forty-three".