21000245 has 16 divisors (see below), whose sum is σ = 29151360. Its totient is φ = 14224704.

The previous prime is 21000233. The next prime is 21000251. The reversal of 21000245 is 54200012.

It is a cyclic number.

It is not a de Polignac number, because 21000245 - 2⁴ = 21000229 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 710 + ... + 6519.

It is an arithmetic number, because the mean of its divisors is an integer number (1821960).

Almost surely, 2^21000245 is an apocalyptic number.

It is an amenable number.

21000245 is a deficient number, since it is larger than the sum of its proper divisors (8151115).

21000245 is an equidigital number, since it uses as much as digits as its factorization.

21000245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7324.

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 21000245 is about 4582.6024265694. The cubic root of 21000245 is about 275.8934905489.

Adding to 21000245 its reverse (54200012), we get a palindrome (75200257).

The spelling of 21000245 in words is "twenty-one million, two hundred forty-five", and thus it is an aban number.