21031825 has 6 divisors (see below), whose sum is σ = 26079494. Its totient is φ = 16825440.

The previous prime is 21031819. The next prime is 21031837. The reversal of 21031825 is 52813012.

It can be written as a sum of positive squares in 3 ways, for example, as 18769 + 21013056 = 137^2 + 4584^2 .

It is not a de Polignac number, because 21031825 - 2³ = 21031817 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21031796 and 21031805.

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 420612 + ... + 420661.

Almost surely, 2^21031825 is an apocalyptic number.

21031825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21031825 is a deficient number, since it is larger than the sum of its proper divisors (5047669).

21031825 is an equidigital number, since it uses as much as digits as its factorization.

21031825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 841283 (or 841278 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21031825 is about 4586.0467725482. The cubic root of 21031825 is about 276.0317167570.

Adding to 21031825 its reverse (52813012), we get a palindrome (73844837).

The spelling of 21031825 in words is "twenty-one million, thirty-one thousand, eight hundred twenty-five".