21510225 has 48 divisors (see below), whose sum is σ = 43122240. Its totient is φ = 10425600.

The previous prime is 21510173. The next prime is 21510227. The reversal of 21510225 is 52201512.

It is not a de Polignac number, because 21510225 - 2⁹ = 21509713 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21510198 and 21510207.

It is not an unprimeable number, because it can be changed into a prime (21510227) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 5977 + ... + 8873.

It is an arithmetic number, because the mean of its divisors is an integer number (898380).

Almost surely, 2^21510225 is an apocalyptic number.

21510225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21510225 is an abundant number, since it is smaller than the sum of its proper divisors (21612015).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21510225 is a wasteful number, since it uses less digits than its factorization.

21510225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2927 (or 2916 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21510225 is about 4637.9117067922. The cubic root of 21510225 is about 278.1089621691.

Adding to 21510225 its reverse (52201512), we get a palindrome (73711737).

It can be divided in two parts, 215 and 10225, that added together give a triangular number (10440 = T₁₄₄).

The spelling of 21510225 in words is "twenty-one million, five hundred ten thousand, two hundred twenty-five".