21220771 has 16 divisors (see below), whose sum is σ = 25740288. Its totient is φ = 17229600.

The previous prime is 21220757. The next prime is 21220783. The reversal of 21220771 is 17702212.

It is a cyclic number.

It is not a de Polignac number, because 21220771 - 2¹⁵ = 21188003 is a prime.

It is a super-2 number, since 2×21220771² = 900642243668882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21220711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2040 + ... + 6826.

It is an arithmetic number, because the mean of its divisors is an integer number (1608768).

Almost surely, 2^21220771 is an apocalyptic number.

21220771 is a deficient number, since it is larger than the sum of its proper divisors (4519517).

21220771 is a wasteful number, since it uses less digits than its factorization.

21220771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4842.

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 21220771 is about 4606.6008075369. The cubic root of 21220771 is about 276.8558595305.

Adding to 21220771 its reverse (17702212), we get a palindrome (38922983).

The spelling of 21220771 in words is "twenty-one million, two hundred twenty thousand, seven hundred seventy-one".