21709800 has 144 divisors (see below), whose sum is σ = 83372640. Its totient is φ = 4959360.

The previous prime is 21709781. The next prime is 21709813. The reversal of 21709800 is 890712.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 11739 + ... + 13461.

Almost surely, 2^21709800 is an apocalyptic number.

21709800 is a gapful number since it is divisible by the number (20) 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 21709800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41686320).

21709800 is an abundant number, since it is smaller than the sum of its proper divisors (61662840).

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

21709800 is a wasteful number, since it uses less digits than its factorization.

21709800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1752 (or 1740 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 21709800 is about 4659.3776408443. The cubic root of 21709800 is about 278.9664275324.

The spelling of 21709800 in words is "twenty-one million, seven hundred nine thousand, eight hundred".