21618201 has 16 divisors (see below), whose sum is σ = 31645440. Its totient is φ = 13018320.

The previous prime is 21618199. The next prime is 21618209. The reversal of 21618201 is 10281612.

It is not a de Polignac number, because 21618201 - 2¹ = 21618199 is a prime.

It is a super-2 number, since 2×21618201² = 934693228952802, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21618209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3370 + ... + 7388.

It is an arithmetic number, because the mean of its divisors is an integer number (1977840).

Almost surely, 2^21618201 is an apocalyptic number.

It is an amenable number.

21618201 is a deficient number, since it is larger than the sum of its proper divisors (10027239).

21618201 is a wasteful number, since it uses less digits than its factorization.

21618201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4196.

The product of its (nonzero) digits is 192, while the sum is 21.

The square root of 21618201 is about 4649.5377189566. The cubic root of 21618201 is about 278.5735317208.

Adding to 21618201 its reverse (10281612), we get a palindrome (31899813).

The spelling of 21618201 in words is "twenty-one million, six hundred eighteen thousand, two hundred one".