21705723 has 12 divisors (see below), whose sum is σ = 33764640. Its totient is φ = 13357296.

The previous prime is 21705703. The next prime is 21705737. The reversal of 21705723 is 32750712.

21705723 is a `hidden beast` number, since 21 + 70 + 572 + 3 = 666.

It is not a de Polignac number, because 21705723 - 2¹³ = 21697531 is a prime.

It is a super-2 number, since 2×21705723² = 942276821905458, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21705703) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 92643 + ... + 92876.

It is an arithmetic number, because the mean of its divisors is an integer number (2813720).

Almost surely, 2^21705723 is an apocalyptic number.

21705723 is a deficient number, since it is larger than the sum of its proper divisors (12058917).

21705723 is a wasteful number, since it uses less digits than its factorization.

21705723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185538 (or 185535 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21705723 is about 4658.9401155198. The cubic root of 21705723 is about 278.9489635710.

The spelling of 21705723 in words is "twenty-one million, seven hundred five thousand, seven hundred twenty-three".