21171156 has 12 divisors (see below), whose sum is σ = 49399392. Its totient is φ = 7057048.

The previous prime is 21171133. The next prime is 21171167. The reversal of 21171156 is 65117112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 882120 + ... + 882143.

It is an arithmetic number, because the mean of its divisors is an integer number (4116616).

Almost surely, 2^21171156 is an apocalyptic number.

It is an amenable number.

21171156 is an abundant number, since it is smaller than the sum of its proper divisors (28228236).

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

21171156 is a wasteful number, since it uses less digits than its factorization.

21171156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1764270 (or 1764268 counting only the distinct ones).

The product of its digits is 420, while the sum is 24.

The square root of 21171156 is about 4601.2124489095. The cubic root of 21171156 is about 276.6399245132.

Adding to 21171156 its reverse (65117112), we get a palindrome (86288268).

The spelling of 21171156 in words is "twenty-one million, one hundred seventy-one thousand, one hundred fifty-six".