21507136 has 56 divisors (see below), whose sum is σ = 49637696. Its totient is φ = 9054720.

The previous prime is 21507133. The next prime is 21507137. The reversal of 21507136 is 63170512.

It is a tau number, because it is divible by the number of its divisors (56).

It is a self number, because there is not a number n which added to its sum of digits gives 21507136.

It is not an unprimeable number, because it can be changed into a prime (21507133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26935 + ... + 27721.

Almost surely, 2^21507136 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 21507136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24818848).

21507136 is an abundant number, since it is smaller than the sum of its proper divisors (28130560).

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

21507136 is an equidigital number, since it uses as much as digits as its factorization.

21507136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 867 (or 857 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21507136 is about 4637.5786785779. The cubic root of 21507136 is about 278.0956488152.

Adding to 21507136 its reverse (63170512), we get a palindrome (84677648).

The spelling of 21507136 in words is "twenty-one million, five hundred seven thousand, one hundred thirty-six".