21242849 has 4 divisors (see below), whose sum is σ = 21325764. Its totient is φ = 21159936.

The previous prime is 21242839. The next prime is 21242857. The reversal of 21242849 is 94824212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17977600 + 3265249 = 4240^2 + 1807^2 .

It is a cyclic number.

It is not a de Polignac number, because 21242849 - 2⁴ = 21242833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21242839) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41072 + ... + 41585.

It is an arithmetic number, because the mean of its divisors is an integer number (5331441).

Almost surely, 2^21242849 is an apocalyptic number.

It is an amenable number.

21242849 is a deficient number, since it is larger than the sum of its proper divisors (82915).

21242849 is an equidigital number, since it uses as much as digits as its factorization.

21242849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82914.

The product of its digits is 9216, while the sum is 32.

The square root of 21242849 is about 4608.9965285298. The cubic root of 21242849 is about 276.9518394725.

Adding to 21242849 its sum of digits (32), we get a square (21242881 = 4609²).

The spelling of 21242849 in words is "twenty-one million, two hundred forty-two thousand, eight hundred forty-nine".