21705393 has 8 divisors (see below), whose sum is σ = 28963008. Its totient is φ = 14459024.

The previous prime is 21705389. The next prime is 21705401. The reversal of 21705393 is 39350712.

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

It is a cyclic number.

It is not a de Polignac number, because 21705393 - 2² = 21705389 is a prime.

It is a super-2 number, since 2×21705393² = 942248170568898, 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 21705393.

It is not an unprimeable number, because it can be changed into a prime (21705323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4180 + ... + 7802.

It is an arithmetic number, because the mean of its divisors is an integer number (3620376).

Almost surely, 2^21705393 is an apocalyptic number.

It is an amenable number.

21705393 is a deficient number, since it is larger than the sum of its proper divisors (7257615).

21705393 is a wasteful number, since it uses less digits than its factorization.

21705393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5623.

The product of its (nonzero) digits is 5670, while the sum is 30.

The square root of 21705393 is about 4658.9046996048. The cubic root of 21705393 is about 278.9475499096.

The spelling of 21705393 in words is "twenty-one million, seven hundred five thousand, three hundred ninety-three".