21666612 has 96 divisors (see below), whose sum is σ = 59512320. Its totient is φ = 6065280.

The previous prime is 21666611. The next prime is 21666637.

21666612 is nontrivially palindromic in base 10.

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21666612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666611) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 132843 + ... + 133005.

It is an arithmetic number, because the mean of its divisors is an integer number (619920).

Almost surely, 2^21666612 is an apocalyptic number.

21666612 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21666612, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29756160).

21666612 is an abundant number, since it is smaller than the sum of its proper divisors (37845708).

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

21666612 is a wasteful number, since it uses less digits than its factorization.

21666612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253 (or 251 counting only the distinct ones).

The product of its digits is 5184, while the sum is 30.

The square root of 21666612 is about 4654.7408091106. The cubic root of 21666612 is about 278.7813191163.

It can be divided in two parts, 2166 and 6612, that added together give a palindrome (8778).

The spelling of 21666612 in words is "twenty-one million, six hundred sixty-six thousand, six hundred twelve".