21107985 has 16 divisors (see below), whose sum is σ = 33918720. Its totient is φ = 11208960.

The previous prime is 21107981. The next prime is 21107987. The reversal of 21107985 is 58970112.

It is not a de Polignac number, because 21107985 - 2² = 21107981 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21107981) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 696 + ... + 6534.

It is an arithmetic number, because the mean of its divisors is an integer number (2119920).

Almost surely, 2^21107985 is an apocalyptic number.

It is an amenable number.

21107985 is a deficient number, since it is larger than the sum of its proper divisors (12810735).

21107985 is a wasteful number, since it uses less digits than its factorization.

21107985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6088.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21107985 is about 4594.3427168639. The cubic root of 21107985 is about 276.3645021267.

The spelling of 21107985 in words is "twenty-one million, one hundred seven thousand, nine hundred eighty-five".