21287376 has 120 divisors (see below), whose sum is σ = 66156480. Its totient is φ = 6336000.

The previous prime is 21287347. The next prime is 21287389. The reversal of 21287376 is 67378212.

21287376 is a `hidden beast` number, since 2 + 1 + 287 + 376 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21287376.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 140901 + ... + 141051.

It is an arithmetic number, because the mean of its divisors is an integer number (551304).

Almost surely, 2^21287376 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 21287376, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33078240).

21287376 is an abundant number, since it is smaller than the sum of its proper divisors (44869104).

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

21287376 is a wasteful number, since it uses less digits than its factorization.

21287376 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265 (or 256 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The square root of 21287376 is about 4613.8244439944. The cubic root of 21287376 is about 277.1452100879.

It can be divided in two parts, 2 and 1287376, that multiplied together give a palindrome (2574752).

The spelling of 21287376 in words is "twenty-one million, two hundred eighty-seven thousand, three hundred seventy-six".