21981193 has 8 divisors (see below), whose sum is σ = 23711688. Its totient is φ = 20256384.

The previous prime is 21981191. The next prime is 21981227. The reversal of 21981193 is 39118912.

It can be written as a sum of positive squares in 4 ways, for example, as 1937664 + 20043529 = 1392^2 + 4477^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21981193 - 2¹ = 21981191 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21981191) 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 7 ways as a sum of consecutive naturals, for example, 10155 + ... + 12127.

It is an arithmetic number, because the mean of its divisors is an integer number (2963961).

Almost surely, 2^21981193 is an apocalyptic number.

It is an amenable number.

21981193 is a deficient number, since it is larger than the sum of its proper divisors (1730495).

21981193 is a wasteful number, since it uses less digits than its factorization.

21981193 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2843.

The product of its digits is 3888, while the sum is 34.

The square root of 21981193 is about 4688.4104982392. The cubic root of 21981193 is about 280.1240649180.

The spelling of 21981193 in words is "twenty-one million, nine hundred eighty-one thousand, one hundred ninety-three".