21217025 has 6 divisors (see below), whose sum is σ = 26309142. Its totient is φ = 16973600.

The previous prime is 21217019. The next prime is 21217033. The reversal of 21217025 is 52071212.

It can be written as a sum of positive squares in 3 ways, for example, as 167281 + 21049744 = 409^2 + 4588^2 .

It is not a de Polignac number, because 21217025 - 2⁶ = 21216961 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21216988 and 21217006.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 424316 + ... + 424365.

It is an arithmetic number, because the mean of its divisors is an integer number (4384857).

Almost surely, 2^21217025 is an apocalyptic number.

21217025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21217025 is a deficient number, since it is larger than the sum of its proper divisors (5092117).

21217025 is an equidigital number, since it uses as much as digits as its factorization.

21217025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 848691 (or 848686 counting only the distinct ones).

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21217025 is about 4606.1941991193. The cubic root of 21217025 is about 276.8395678968.

Adding to 21217025 its reverse (52071212), we get a palindrome (73288237).

The spelling of 21217025 in words is "twenty-one million, two hundred seventeen thousand, twenty-five".