21638201 has 8 divisors (see below), whose sum is σ = 23871624. Its totient is φ = 19486080.

The previous prime is 21638167. The next prime is 21638203. The reversal of 21638201 is 10283612.

It can be written as a sum of positive squares in 4 ways, for example, as 1207801 + 20430400 = 1099^2 + 4520^2 .

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 21638201 - 2¹⁰ = 21637177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21638203) 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, 19766 + ... + 20831.

It is an arithmetic number, because the mean of its divisors is an integer number (2983953).

Almost surely, 2^21638201 is an apocalyptic number.

It is an amenable number.

21638201 is a deficient number, since it is larger than the sum of its proper divisors (2233423).

21638201 is a wasteful number, since it uses less digits than its factorization.

21638201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40651.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21638201 is about 4651.6879731985. The cubic root of 21638201 is about 278.6594123386.

The spelling of 21638201 in words is "twenty-one million, six hundred thirty-eight thousand, two hundred one".