21197985 has 16 divisors (see below), whose sum is σ = 35087040. Its totient is φ = 10915520.

The previous prime is 21197947. The next prime is 21197989. The reversal of 21197985 is 58979112.

It is not a de Polignac number, because 21197985 - 2⁶ = 21197921 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21197989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23931 + ... + 24800.

It is an arithmetic number, because the mean of its divisors is an integer number (2192940).

Almost surely, 2^21197985 is an apocalyptic number.

It is an amenable number.

21197985 is a deficient number, since it is larger than the sum of its proper divisors (13889055).

21197985 is a wasteful number, since it uses less digits than its factorization.

21197985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48768.

The product of its digits is 45360, while the sum is 42.

The square root of 21197985 is about 4604.1269530716. The cubic root of 21197985 is about 276.7567318586.

The spelling of 21197985 in words is "twenty-one million, one hundred ninety-seven thousand, nine hundred eighty-five".