21201606 has 48 divisors (see below), whose sum is σ = 49420800. Its totient is φ = 6547824.

The previous prime is 21201599. The next prime is 21201611. The reversal of 21201606 is 60610212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15415 + ... + 16733.

It is an arithmetic number, because the mean of its divisors is an integer number (1029600).

Almost surely, 2^21201606 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21201606, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24710400).

21201606 is an abundant number, since it is smaller than the sum of its proper divisors (28219194).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21201606 is a wasteful number, since it uses less digits than its factorization.

21201606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1393 (or 1390 counting only the distinct ones).

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

The square root of 21201606 is about 4604.5201704412. The cubic root of 21201606 is about 276.7724893165.

Adding to 21201606 its reverse (60610212), we get a palindrome (81811818).

The spelling of 21201606 in words is "twenty-one million, two hundred one thousand, six hundred six".