21221205625 has 15 divisors (see below), whose sum is σ = 26522570217. Its totient is φ = 16974051000.

The previous prime is 21221205617. The next prime is 21221205641. The reversal of 21221205625 is 52650212212.

The square root of 21221205625 is 145675.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 2 ways, for example, as 1663742521 + 19557463104 = 40789^2 + 139848^2 .

It is not a de Polignac number, because 21221205625 - 2³ = 21221205617 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221205593 and 21221205602.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 3638962 + ... + 3644788.

Almost surely, 2^21221205625 is an apocalyptic number.

21221205625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21221205625 is the 145675-th square number.

21221205625 is the 72838-th centered octagonal number.

It is an amenable number.

21221205625 is a deficient number, since it is larger than the sum of its proper divisors (5301364592).

21221205625 is an frugal number, since it uses more digits than its factorization.

21221205625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11674 (or 5832 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 28.

Adding to 21221205625 its reverse (52650212212), we get a palindrome (73871417837).

The spelling of 21221205625 in words is "twenty-one billion, two hundred twenty-one million, two hundred five thousand, six hundred twenty-five".