21612006 has 48 divisors (see below), whose sum is σ = 53093040. Its totient is φ = 6298560.

The previous prime is 21611999. The next prime is 21612011. The reversal of 21612006 is 60021612.

It is a happy number.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21612006.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 2016 + ... + 6876.

It is an arithmetic number, because the mean of its divisors is an integer number (1106105).

Almost surely, 2^21612006 is an apocalyptic number.

21612006 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21612006, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26546520).

21612006 is an abundant number, since it is smaller than the sum of its proper divisors (31481034).

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

21612006 is a wasteful number, since it uses less digits than its factorization.

21612006 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4901 (or 4898 counting only the distinct ones).

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

The square root of 21612006 is about 4648.8714759606. The cubic root of 21612006 is about 278.5469194554.

Adding to 21612006 its reverse (60021612), we get a palindrome (81633618).

The spelling of 21612006 in words is "twenty-one million, six hundred twelve thousand, six".