21251136 has 56 divisors (see below), whose sum is σ = 56676544. Its totient is φ = 7027200.

The previous prime is 21251129. The next prime is 21251137. The reversal of 21251136 is 63115212.

It is a super-2 number, since 2×21251136² = 903221562580992, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21251137) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28626 + ... + 29358.

Almost surely, 2^21251136 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 21251136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28338272).

21251136 is an abundant number, since it is smaller than the sum of its proper divisors (35425408).

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

21251136 is a wasteful number, since it uses less digits than its factorization.

21251136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 899 (or 889 counting only the distinct ones).

The product of its digits is 360, while the sum is 21.

The square root of 21251136 is about 4609.8954434998. The cubic root of 21251136 is about 276.9878484767.

Adding to 21251136 its reverse (63115212), we get a palindrome (84366348).

The spelling of 21251136 in words is "twenty-one million, two hundred fifty-one thousand, one hundred thirty-six".