21705742 has 8 divisors (see below), whose sum is σ = 32581656. Its totient is φ = 10845192.

The previous prime is 21705737. The next prime is 21705743. The reversal of 21705742 is 24750712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21705742² = 942278471541128, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21705742.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 828 + ... + 6640.

It is an arithmetic number, because the mean of its divisors is an integer number (4072707).

Almost surely, 2^21705742 is an apocalyptic number.

21705742 is a deficient number, since it is larger than the sum of its proper divisors (10875914).

21705742 is a wasteful number, since it uses less digits than its factorization.

21705742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7682.

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21705742 is about 4658.9421546098. The cubic root of 21705742 is about 278.9490449632.

The spelling of 21705742 in words is "twenty-one million, seven hundred five thousand, seven hundred forty-two".