21128436 has 36 divisors (see below), whose sum is σ = 61038432. Its totient is φ = 6036624.

The previous prime is 21128411. The next prime is 21128441. The reversal of 21128436 is 63482112.

It is a tau number, because it is divible by the number of its divisors (36).

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 11 ways as a sum of consecutive naturals, for example, 41670 + ... + 42173.

It is an arithmetic number, because the mean of its divisors is an integer number (1695512).

Almost surely, 2^21128436 is an apocalyptic number.

It is an amenable number.

21128436 is an abundant number, since it is smaller than the sum of its proper divisors (39909996).

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

21128436 is a wasteful number, since it uses less digits than its factorization.

21128436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83860 (or 83855 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21128436 is about 4596.5678500377. The cubic root of 21128436 is about 276.4537275403.

The spelling of 21128436 in words is "twenty-one million, one hundred twenty-eight thousand, four hundred thirty-six".