21131156 has 6 divisors (see below), whose sum is σ = 36979530. Its totient is φ = 10565576.

The previous prime is 21131147. The next prime is 21131161. The reversal of 21131156 is 65113112.

It can be written as a sum of positive squares in only one way, i.e., 16679056 + 4452100 = 4084^2 + 2110^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2641391 + ... + 2641398.

It is an arithmetic number, because the mean of its divisors is an integer number (6163255).

Almost surely, 2^21131156 is an apocalyptic number.

It is an amenable number.

21131156 is a deficient number, since it is larger than the sum of its proper divisors (15848374).

21131156 is a wasteful number, since it uses less digits than its factorization.

21131156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5282793 (or 5282791 counting only the distinct ones).

The product of its digits is 180, while the sum is 20.

The square root of 21131156 is about 4596.8637134464. The cubic root of 21131156 is about 276.4655902557.

Adding to 21131156 its reverse (65113112), we get a palindrome (86244268).

The spelling of 21131156 in words is "twenty-one million, one hundred thirty-one thousand, one hundred fifty-six".