21531136 has 40 divisors (see below), whose sum is σ = 46943424. Its totient is φ = 9784320.

The previous prime is 21531127. The next prime is 21531149. The reversal of 21531136 is 63113512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3721 + ... + 7543.

Almost surely, 2^21531136 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 21531136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23471712).

21531136 is an abundant number, since it is smaller than the sum of its proper divisors (25412288).

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

21531136 is an equidigital number, since it uses as much as digits as its factorization.

21531136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3852 (or 3836 counting only the distinct ones).

The product of its digits is 540, while the sum is 22.

The square root of 21531136 is about 4640.1655142893. The cubic root of 21531136 is about 278.1990534786.

Adding to 21531136 its reverse (63113512), we get a palindrome (84644648).

The spelling of 21531136 in words is "twenty-one million, five hundred thirty-one thousand, one hundred thirty-six".