21705712 has 40 divisors (see below), whose sum is σ = 49191296. Its totient is φ = 9084096.

The previous prime is 21705703. The next prime is 21705737. The reversal of 21705712 is 21750712.

It is a happy number.

It is a super-2 number, since 2×21705712² = 942275866853888, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2563 + ... + 7069.

Almost surely, 2^21705712 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 21705712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24595648).

21705712 is an abundant number, since it is smaller than the sum of its proper divisors (27485584).

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

21705712 is a wasteful number, since it uses less digits than its factorization.

21705712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4565 (or 4559 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21705712 is about 4658.9389349937. The cubic root of 21705712 is about 278.9489164492.

The spelling of 21705712 in words is "twenty-one million, seven hundred five thousand, seven hundred twelve".