21005727 has 16 divisors (see below), whose sum is σ = 29756160. Its totient is φ = 13135232.

The previous prime is 21005713. The next prime is 21005737. The reversal of 21005727 is 72750012.

It is a cyclic number.

It is not a de Polignac number, because 21005727 - 2¹⁴ = 20989343 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21005697 and 21005706.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005707) 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 15 ways as a sum of consecutive naturals, for example, 20878 + ... + 21860.

It is an arithmetic number, because the mean of its divisors is an integer number (1859760).

Almost surely, 2^21005727 is an apocalyptic number.

21005727 is a deficient number, since it is larger than the sum of its proper divisors (8750433).

21005727 is a wasteful number, since it uses less digits than its factorization.

21005727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1422.

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 21005727 is about 4583.2005192878. The cubic root of 21005727 is about 275.9174952931.

Adding to 21005727 its reverse (72750012), we get a palindrome (93755739).

The spelling of 21005727 in words is "twenty-one million, five thousand, seven hundred twenty-seven".