21041705 has 4 divisors (see below), whose sum is σ = 25250052. Its totient is φ = 16833360.

The previous prime is 21041677. The next prime is 21041707. The reversal of 21041705 is 50714012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4631104 + 16410601 = 2152^2 + 4051^2 .

It is not a de Polignac number, because 21041705 - 2¹⁰ = 21040681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21041707) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2104166 + ... + 2104175.

It is an arithmetic number, because the mean of its divisors is an integer number (6312513).

Almost surely, 2^21041705 is an apocalyptic number.

It is an amenable number.

21041705 is a deficient number, since it is larger than the sum of its proper divisors (4208347).

21041705 is an equidigital number, since it uses as much as digits as its factorization.

21041705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4208346.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21041705 is about 4587.1238265388. The cubic root of 21041705 is about 276.0749332702.

Adding to 21041705 its reverse (50714012), we get a palindrome (71755717).

The spelling of 21041705 in words is "twenty-one million, forty-one thousand, seven hundred five".