21284125 has 16 divisors (see below), whose sum is σ = 27217008. Its totient is φ = 16608000.

The previous prime is 21284117. The next prime is 21284129. The reversal of 21284125 is 52148212.

It can be written as a sum of positive squares in 8 ways, for example, as 18844281 + 2439844 = 4341^2 + 1562^2 .

It is not a de Polignac number, because 21284125 - 2³ = 21284117 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21284125.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21284129) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 3049 + ... + 7201.

It is an arithmetic number, because the mean of its divisors is an integer number (1701063).

Almost surely, 2^21284125 is an apocalyptic number.

21284125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21284125 is a deficient number, since it is larger than the sum of its proper divisors (5932883).

21284125 is an equidigital number, since it uses as much as digits as its factorization.

21284125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4209 (or 4199 counting only the distinct ones).

The product of its digits is 1280, while the sum is 25.

The square root of 21284125 is about 4613.4721197814. The cubic root of 21284125 is about 277.1311008658.

The spelling of 21284125 in words is "twenty-one million, two hundred eighty-four thousand, one hundred twenty-five".