21808616 has 16 divisors (see below), whose sum is σ = 40948740. Its totient is φ = 10888960.

The previous prime is 21808613. The next prime is 21808621. The reversal of 21808616 is 61680812.

It can be written as a sum of positive squares in 2 ways, for example, as 21252100 + 556516 = 4610^2 + 746^2 .

It is not an unprimeable number, because it can be changed into a prime (21808613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6080 + ... + 8976.

Almost surely, 2^21808616 is an apocalyptic number.

It is an amenable number.

21808616 is a deficient number, since it is larger than the sum of its proper divisors (19140124).

21808616 is a wasteful number, since it uses less digits than its factorization.

21808616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3844 (or 3840 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21808616 is about 4669.9695930488. The cubic root of 21808616 is about 279.3890420133.

The spelling of 21808616 in words is "twenty-one million, eight hundred eight thousand, six hundred sixteen".