21000244 has 12 divisors (see below), whose sum is σ = 38684800. Its totient is φ = 9947448.

The previous prime is 21000233. The next prime is 21000251. The reversal of 21000244 is 44200012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138084 + ... + 138235.

Almost surely, 2^21000244 is an apocalyptic number.

It is an amenable number.

21000244 is a deficient number, since it is larger than the sum of its proper divisors (17684556).

21000244 is a wasteful number, since it uses less digits than its factorization.

21000244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 276342 (or 276340 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 21000244 is about 4582.6023174611. The cubic root of 21000244 is about 275.8934861697.

Adding to 21000244 its reverse (44200012), we get a palindrome (65200256).

The spelling of 21000244 in words is "twenty-one million, two hundred forty-four", and thus it is an aban number.