21771156 has 96 divisors (see below), whose sum is σ = 59222016. Its totient is φ = 6160000.

The previous prime is 21771151. The next prime is 21771157. The reversal of 21771156 is 65117712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771151) 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 31 ways as a sum of consecutive naturals, for example, 215506 + ... + 215606.

It is an arithmetic number, because the mean of its divisors is an integer number (616896).

Almost surely, 2^21771156 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21771156, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29611008).

21771156 is an abundant number, since it is smaller than the sum of its proper divisors (37450860).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21771156 is a wasteful number, since it uses less digits than its factorization.

21771156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213 (or 211 counting only the distinct ones).

The product of its digits is 2940, while the sum is 30.

The square root of 21771156 is about 4665.9571365369. The cubic root of 21771156 is about 279.2289843009.

Adding to 21771156 its reverse (65117712), we get a palindrome (86888868).

It can be divided in two parts, 2177 and 1156, that added together give a palindrome (3333).

The spelling of 21771156 in words is "twenty-one million, seven hundred seventy-one thousand, one hundred fifty-six".