21251384 has 32 divisors (see below), whose sum is σ = 49680000. Its totient is φ = 8279520.

The previous prime is 21251383. The next prime is 21251389. The reversal of 21251384 is 48315212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16634 + ... + 17865.

It is an arithmetic number, because the mean of its divisors is an integer number (1552500).

Almost surely, 2^21251384 is an apocalyptic number.

It is an amenable number.

21251384 is an abundant number, since it is smaller than the sum of its proper divisors (28428616).

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

21251384 is a wasteful number, since it uses less digits than its factorization.

21251384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34523 (or 34519 counting only the distinct ones).

The product of its digits is 1920, while the sum is 26.

The square root of 21251384 is about 4609.9223420791. The cubic root of 21251384 is about 276.9889259519.

Adding to 21251384 its reverse (48315212), we get a palindrome (69566596).

The spelling of 21251384 in words is "twenty-one million, two hundred fifty-one thousand, three hundred eighty-four".