21020985 has 32 divisors (see below), whose sum is σ = 38177280. Its totient is φ = 10969344.

The previous prime is 21020971. The next prime is 21021001. The reversal of 21020985 is 58902012.

It is not a de Polignac number, because 21020985 - 2¹⁰ = 21019961 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4689 + ... + 8001.

It is an arithmetic number, because the mean of its divisors is an integer number (1193040).

Almost surely, 2^21020985 is an apocalyptic number.

It is an amenable number.

21020985 is a deficient number, since it is larger than the sum of its proper divisors (17156295).

21020985 is a wasteful number, since it uses less digits than its factorization.

21020985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3374 (or 3368 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 21020985 is about 4584.8647744508. The cubic root of 21020985 is about 275.9842854947.

Adding to 21020985 its reverse (58902012), we get a palindrome (79922997).

The spelling of 21020985 in words is "twenty-one million, twenty thousand, nine hundred eighty-five".