21024649 has 4 divisors (see below), whose sum is σ = 21046036. Its totient is φ = 21003264.

The previous prime is 21024643. The next prime is 21024743. The reversal of 21024649 is 94642012.

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 15264649 + 5760000 = 3907^2 + 2400^2 .

It is a cyclic number.

It is not a de Polignac number, because 21024649 - 2⁵ = 21024617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21024643) 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, 9144 + ... + 11209.

It is an arithmetic number, because the mean of its divisors is an integer number (5261509).

Almost surely, 2^21024649 is an apocalyptic number.

It is an amenable number.

21024649 is a deficient number, since it is larger than the sum of its proper divisors (21387).

21024649 is a wasteful number, since it uses less digits than its factorization.

21024649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21386.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21024649 is about 4585.2643326203. The cubic root of 21024649 is about 276.0003194353. Note that the first 3 decimals are identical.

The spelling of 21024649 in words is "twenty-one million, twenty-four thousand, six hundred forty-nine".