21205625 has 40 divisors (see below), whose sum is σ = 31339968. Its totient is φ = 14040000.

The previous prime is 21205621. The next prime is 21205633. The reversal of 21205625 is 52650212.

It is not a de Polignac number, because 21205625 - 2² = 21205621 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21205625.

It is not an unprimeable number, because it can be changed into a prime (21205621) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 161810 + ... + 161940.

Almost surely, 2^21205625 is an apocalyptic number.

21205625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21205625 is a deficient number, since it is larger than the sum of its proper divisors (10134343).

21205625 is an equidigital number, since it uses as much as digits as its factorization.

21205625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195 (or 180 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 21205625 is about 4604.9565687420. The cubic root of 21205625 is about 276.7899766451.

Adding to 21205625 its reverse (52650212), we get a palindrome (73855837).

The spelling of 21205625 in words is "twenty-one million, two hundred five thousand, six hundred twenty-five".