21287436 has 48 divisors (see below), whose sum is σ = 51166080. Its totient is φ = 6885760.

The previous prime is 21287423. The next prime is 21287437. The reversal of 21287436 is 63478212.

It is a junction number, because it is equal to n+sod(n) for n = 21287397 and 21287406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287437) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75616 + ... + 75896.

It is an arithmetic number, because the mean of its divisors is an integer number (1065960).

Almost surely, 2^21287436 is an apocalyptic number.

It is an amenable number.

21287436 is an abundant number, since it is smaller than the sum of its proper divisors (29878644).

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

21287436 is a wasteful number, since it uses less digits than its factorization.

21287436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454 (or 452 counting only the distinct ones).

The product of its digits is 16128, while the sum is 33.

The square root of 21287436 is about 4613.8309461878. The cubic root of 21287436 is about 277.1454704722.

The spelling of 21287436 in words is "twenty-one million, two hundred eighty-seven thousand, four hundred thirty-six".