21020161800625 has 45 divisors (see below), whose sum is σ = 28444757991111. Its totient is φ = 15521480676000.

The previous prime is 21020161800587. The next prime is 21020161800641. The reversal of 21020161800625 is 52600816102012.

It is a happy number.

The square root of 21020161800625 is 4584775.

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

It can be written as a sum of positive squares in 7 ways, for example, as 20762248146721 + 257913653904 = 4556561^2 + 507852^2 .

It is not a de Polignac number, because 21020161800625 - 2⁷ = 21020161800497 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 1490044822 + ... + 1490058928.

Almost surely, 2^{21020161800625} is an apocalyptic number.

21020161800625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21020161800625 is the 4584775-th square number.

21020161800625 is the 2292388-th centered octagonal number.

It is an amenable number.

21020161800625 is a deficient number, since it is larger than the sum of its proper divisors (7424596190486).

21020161800625 is an frugal number, since it uses more digits than its factorization.

21020161800625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28260 (or 14125 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 34.

Adding to 21020161800625 its reverse (52600816102012), we get a palindrome (73620977902637).

The spelling of 21020161800625 in words is "twenty-one trillion, twenty billion, one hundred sixty-one million, eight hundred thousand, six hundred twenty-five".