21385705 has 16 divisors (see below), whose sum is σ = 28594944. Its totient is φ = 15220480.

The previous prime is 21385703. The next prime is 21385709. The reversal of 21385705 is 50758312.

It is not a de Polignac number, because 21385705 - 2¹ = 21385703 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21385703) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1552 + ... + 6721.

It is an arithmetic number, because the mean of its divisors is an integer number (1787184).

Almost surely, 2^21385705 is an apocalyptic number.

It is an amenable number.

21385705 is a deficient number, since it is larger than the sum of its proper divisors (7209239).

21385705 is a wasteful number, since it uses less digits than its factorization.

21385705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8336.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21385705 is about 4624.4680775198. The cubic root of 21385705 is about 277.5712773104.

The spelling of 21385705 in words is "twenty-one million, three hundred eighty-five thousand, seven hundred five".