21006771 has 4 divisors (see below), whose sum is σ = 28009032. Its totient is φ = 14004512.

The previous prime is 21006743. The next prime is 21006779. The reversal of 21006771 is 17760012.

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

It is a cyclic number.

It is not a de Polignac number, because 21006771 - 2⁶ = 21006707 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21006779) 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, 3501126 + ... + 3501131.

It is an arithmetic number, because the mean of its divisors is an integer number (7002258).

Almost surely, 2^21006771 is an apocalyptic number.

21006771 is a deficient number, since it is larger than the sum of its proper divisors (7002261).

21006771 is an equidigital number, since it uses as much as digits as its factorization.

21006771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7002260.

The product of its (nonzero) digits is 588, while the sum is 24.

The square root of 21006771 is about 4583.3144120822. The cubic root of 21006771 is about 275.9220663178.

Adding to 21006771 its reverse (17760012), we get a palindrome (38766783).

The spelling of 21006771 in words is "twenty-one million, six thousand, seven hundred seventy-one".