21709608 has 64 divisors (see below), whose sum is σ = 57576960. Its totient is φ = 6806976.

The previous prime is 21709601. The next prime is 21709613. The reversal of 21709608 is 80690712.

It is not an unprimeable number, because it can be changed into a prime (21709601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36691 + ... + 37277.

It is an arithmetic number, because the mean of its divisors is an integer number (899640).

Almost surely, 2^21709608 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 21709608, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28788480).

21709608 is an abundant number, since it is smaller than the sum of its proper divisors (35867352).

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

21709608 is a wasteful number, since it uses less digits than its factorization.

21709608 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 686 (or 682 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 33.

The square root of 21709608 is about 4659.3570371887. The cubic root of 21709608 is about 278.9656051432.

The spelling of 21709608 in words is "twenty-one million, seven hundred nine thousand, six hundred eight".