21993185 has 4 divisors (see below), whose sum is σ = 26391828. Its totient is φ = 17594544.

The previous prime is 21993161. The next prime is 21993187. The reversal of 21993185 is 58139912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13184161 + 8809024 = 3631^2 + 2968^2 .

It is a cyclic number.

It is not a de Polignac number, because 21993185 - 2¹⁰ = 21992161 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21993187) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2199314 + ... + 2199323.

It is an arithmetic number, because the mean of its divisors is an integer number (6597957).

Almost surely, 2^21993185 is an apocalyptic number.

It is an amenable number.

21993185 is a deficient number, since it is larger than the sum of its proper divisors (4398643).

21993185 is an equidigital number, since it uses as much as digits as its factorization.

21993185 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4398642.

The product of its digits is 19440, while the sum is 38.

The square root of 21993185 is about 4689.6892221127. The cubic root of 21993185 is about 280.1749968986.

The spelling of 21993185 in words is "twenty-one million, nine hundred ninety-three thousand, one hundred eighty-five".