21000985 has 32 divisors (see below), whose sum is σ = 27941760. Its totient is φ = 15095808.

The previous prime is 21000983. The next prime is 21001021. The reversal of 21000985 is 58900012.

It is a cyclic number.

It is not a de Polignac number, because 21000985 - 2¹ = 21000983 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21000983) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 216457 + ... + 216553.

It is an arithmetic number, because the mean of its divisors is an integer number (873180).

Almost surely, 2^21000985 is an apocalyptic number.

It is an amenable number.

21000985 is a deficient number, since it is larger than the sum of its proper divisors (6940775).

21000985 is a wasteful number, since it uses less digits than its factorization.

21000985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 21000985 is about 4582.6831660066. The cubic root of 21000985 is about 275.8967311267.

Adding to 21000985 its reverse (58900012), we get a palindrome (79900997).

The spelling of 21000985 in words is "twenty-one million, nine hundred eighty-five", and thus it is an aban number.