21709860 has 48 divisors (see below), whose sum is σ = 61943616. Its totient is φ = 5679232.

The previous prime is 21709847. The next prime is 21709879. The reversal of 21709860 is 6890712.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 234 + ... + 6593.

It is an arithmetic number, because the mean of its divisors is an integer number (1290492).

Almost surely, 2^21709860 is an apocalyptic number.

21709860 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 21709860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30971808).

21709860 is an abundant number, since it is smaller than the sum of its proper divisors (40233756).

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

21709860 is a wasteful number, since it uses less digits than its factorization.

21709860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6892 (or 6890 counting only the distinct ones).

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

The square root of 21709860 is about 4659.3840794680. The cubic root of 21709860 is about 278.9666845280.

The spelling of 21709860 in words is "twenty-one million, seven hundred nine thousand, eight hundred sixty".