21206625 has 64 divisors (see below), whose sum is σ = 39626496. Its totient is φ = 9984000.

The previous prime is 21206623. The next prime is 21206657. The reversal of 21206625 is 52660212.

It is not a de Polignac number, because 21206625 - 2¹ = 21206623 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21206595 and 21206604.

It is not an unprimeable number, because it can be changed into a prime (21206623) by changing a digit.

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 63 ways as a sum of consecutive naturals, for example, 218577 + ... + 218673.

It is an arithmetic number, because the mean of its divisors is an integer number (619164).

Almost surely, 2^21206625 is an apocalyptic number.

21206625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21206625 is a deficient number, since it is larger than the sum of its proper divisors (18419871).

21206625 is a wasteful number, since it uses less digits than its factorization.

21206625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 179 (or 169 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21206625 is about 4605.0651461190. The cubic root of 21206625 is about 276.7943274660.

Adding to 21206625 its reverse (52660212), we get a palindrome (73866837).

The spelling of 21206625 in words is "twenty-one million, two hundred six thousand, six hundred twenty-five".