21206601 has 12 divisors (see below), whose sum is σ = 32988228. Its totient is φ = 13050144.

The previous prime is 21206593. The next prime is 21206609. The reversal of 21206601 is 10660212.

It is a happy number.

21206601 is a `hidden beast` number, since 2 + 1 + 2 + 0 + 660 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (21206593) and next prime (21206609).

It can be written as a sum of positive squares in 2 ways, for example, as 3059001 + 18147600 = 1749^2 + 4260^2 .

It is not a de Polignac number, because 21206601 - 2³ = 21206593 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21206609) 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 11 ways as a sum of consecutive naturals, for example, 90510 + ... + 90743.

It is an arithmetic number, because the mean of its divisors is an integer number (2749019).

Almost surely, 2^21206601 is an apocalyptic number.

It is an amenable number.

21206601 is a deficient number, since it is larger than the sum of its proper divisors (11781627).

21206601 is a wasteful number, since it uses less digits than its factorization.

21206601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181272 (or 181269 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21206601 is about 4605.0625402919. The cubic root of 21206601 is about 276.7942230479.

Adding to 21206601 its reverse (10660212), we get a palindrome (31866813).

The spelling of 21206601 in words is "twenty-one million, two hundred six thousand, six hundred one".