21608861 has 4 divisors (see below), whose sum is σ = 22068672. Its totient is φ = 21149052.

The previous prime is 21608837. The next prime is 21608893. The reversal of 21608861 is 16880612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21608861 - 2²² = 17414557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21608831) 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, 229835 + ... + 229928.

It is an arithmetic number, because the mean of its divisors is an integer number (5517168).

Almost surely, 2^21608861 is an apocalyptic number.

It is an amenable number.

21608861 is a deficient number, since it is larger than the sum of its proper divisors (459811).

21608861 is an equidigital number, since it uses as much as digits as its factorization.

21608861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 459810.

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

The square root of 21608861 is about 4648.5332095189. The cubic root of 21608861 is about 278.5334073277.

The spelling of 21608861 in words is "twenty-one million, six hundred eight thousand, eight hundred sixty-one".