21210449 has 4 divisors (see below), whose sum is σ = 22842036. Its totient is φ = 19578864.

The previous prime is 21210433. The next prime is 21210461. The reversal of 21210449 is 94401212.

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 7756225 + 13454224 = 2785^2 + 3668^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210449 - 2⁴ = 21210433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 815774 + ... + 815799.

It is an arithmetic number, because the mean of its divisors is an integer number (5710509).

Almost surely, 2^21210449 is an apocalyptic number.

It is an amenable number.

21210449 is a deficient number, since it is larger than the sum of its proper divisors (1631587).

21210449 is a wasteful number, since it uses less digits than its factorization.

21210449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1631586.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21210449 is about 4605.4803223985. The cubic root of 21210449 is about 276.8109637435.

The spelling of 21210449 in words is "twenty-one million, two hundred ten thousand, four hundred forty-nine".