21253784 has 16 divisors (see below), whose sum is σ = 39904800. Its totient is φ = 10612512.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253784 is 48735212.

It is a self number, because there is not a number n which added to its sum of digits gives 21253784.

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, 7034 + ... + 9590.

It is an arithmetic number, because the mean of its divisors is an integer number (2494050).

Almost surely, 2^21253784 is an apocalyptic number.

It is an amenable number.

21253784 is a deficient number, since it is larger than the sum of its proper divisors (18651016).

21253784 is a wasteful number, since it uses less digits than its factorization.

21253784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3602 (or 3598 counting only the distinct ones).

The product of its digits is 13440, while the sum is 32.

The square root of 21253784 is about 4610.1826428028. The cubic root of 21253784 is about 276.9993526987. Note that the first 3 decimals are identical.

Adding to 21253784 its reverse (48735212), we get a palindrome (69988996).

The spelling of 21253784 in words is "twenty-one million, two hundred fifty-three thousand, seven hundred eighty-four".