21238549 has 2 divisors, whose sum is σ = 21238550. Its totient is φ = 21238548.

The previous prime is 21238543. The next prime is 21238571. The reversal of 21238549 is 94583212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15444900 + 5793649 = 3930^2 + 2407^2 .

It is a cyclic number.

It is not a de Polignac number, because 21238549 - 2¹⁵ = 21205781 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21238543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10619274 + 10619275.

It is an arithmetic number, because the mean of its divisors is an integer number (10619275).

Almost surely, 2^21238549 is an apocalyptic number.

It is an amenable number.

21238549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21238549 is an equidigital number, since it uses as much as digits as its factorization.

21238549 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 34.

The square root of 21238549 is about 4608.5300259410. The cubic root of 21238549 is about 276.9331512499.

The spelling of 21238549 in words is "twenty-one million, two hundred thirty-eight thousand, five hundred forty-nine".