21003606 has 24 divisors (see below), whose sum is σ = 49008960. Its totient is φ = 6462576.

The previous prime is 21003601. The next prime is 21003637. The reversal of 21003606 is 60630012.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003601) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 44646 + ... + 45113.

It is an arithmetic number, because the mean of its divisors is an integer number (2042040).

Almost surely, 2^21003606 is an apocalyptic number.

21003606 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21003606 is an abundant number, since it is smaller than the sum of its proper divisors (28005354).

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

21003606 is a wasteful number, since it uses less digits than its factorization.

21003606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89780 (or 89777 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21003606 is about 4582.9691249233. The cubic root of 21003606 is about 275.9082082908.

Adding to 21003606 its reverse (60630012), we get a palindrome (81633618).

It can be divided in two parts, 21003 and 606, that added together give a square (21609 = 147²).

The spelling of 21003606 in words is "twenty-one million, three thousand, six hundred six".