21316825 has 6 divisors (see below), whose sum is σ = 26432894. Its totient is φ = 17053440.

The previous prime is 21316819. The next prime is 21316831. The reversal of 21316825 is 52861312.

It is an interprime number because it is at equal distance from previous prime (21316819) and next prime (21316831).

It can be written as a sum of positive squares in 3 ways, for example, as 404496 + 20912329 = 636^2 + 4573^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21316825 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21316793 and 21316802.

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, 426312 + ... + 426361.

Almost surely, 2^21316825 is an apocalyptic number.

21316825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21316825 is a deficient number, since it is larger than the sum of its proper divisors (5116069).

21316825 is an equidigital number, since it uses as much as digits as its factorization.

21316825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 852683 (or 852678 counting only the distinct ones).

The product of its digits is 2880, while the sum is 28.

The square root of 21316825 is about 4617.0147281550. The cubic root of 21316825 is about 277.2729522854.

The spelling of 21316825 in words is "twenty-one million, three hundred sixteen thousand, eight hundred twenty-five".