21641616 has 60 divisors (see below), whose sum is σ = 61064172. Its totient is φ = 7154688.

The previous prime is 21641611. The next prime is 21641671. The reversal of 21641616 is 61614612.

21641616 is a `hidden beast` number, since 2 + 1 + 6 + 41 + 616 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 9363600 + 12278016 = 3060^2 + 3504^2 .

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 21641616.

It is not an unprimeable number, because it can be changed into a prime (21641611) 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, 19180 + ... + 20276.

Almost surely, 2^21641616 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21641616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30532086).

21641616 is an abundant number, since it is smaller than the sum of its proper divisors (39422556).

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

21641616 is a wasteful number, since it uses less digits than its factorization.

21641616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1248 (or 1239 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21641616 is about 4652.0550297691. The cubic root of 21641616 is about 278.6740711641.

The spelling of 21641616 in words is "twenty-one million, six hundred forty-one thousand, six hundred sixteen".