21216425 has 12 divisors (see below), whose sum is σ = 27856476. Its totient is φ = 15974400.

The previous prime is 21216413. The next prime is 21216427. The reversal of 21216425 is 52461212.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 1038361 + 20178064 = 1019^2 + 4492^2 .

It is not a de Polignac number, because 21216425 - 2⁴ = 21216409 is a prime.

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 21216425.

It is not an unprimeable number, because it can be changed into a prime (21216427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 24536 + ... + 25385.

It is an arithmetic number, because the mean of its divisors is an integer number (2321373).

Almost surely, 2^21216425 is an apocalyptic number.

21216425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21216425 is a deficient number, since it is larger than the sum of its proper divisors (6640051).

21216425 is a wasteful number, since it uses less digits than its factorization.

21216425 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49948 (or 49943 counting only the distinct ones).

The product of its digits is 960, while the sum is 23.

The square root of 21216425 is about 4606.1290689689. The cubic root of 21216425 is about 276.8369582739.

Adding to 21216425 its reverse (52461212), we get a palindrome (73677637).

The spelling of 21216425 in words is "twenty-one million, two hundred sixteen thousand, four hundred twenty-five".