21251020633 has 4 divisors (see below), whose sum is σ = 21825372580. Its totient is φ = 20676668688.

The previous prime is 21251020631. The next prime is 21251020673. The reversal of 21251020633 is 33602015212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11250420624 + 10000600009 = 106068^2 + 100003^2 .

It is a cyclic number.

It is not a de Polignac number, because 21251020633 - 2¹ = 21251020631 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21251020598 and 21251020607.

It is not an unprimeable number, because it can be changed into a prime (21251020631) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 287175918 + ... + 287175991.

It is an arithmetic number, because the mean of its divisors is an integer number (5456343145).

Almost surely, 2^21251020633 is an apocalyptic number.

It is an amenable number.

21251020633 is a deficient number, since it is larger than the sum of its proper divisors (574351947).

21251020633 is an equidigital number, since it uses as much as digits as its factorization.

21251020633 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 574351946.

The product of its (nonzero) digits is 2160, while the sum is 25.

Adding to 21251020633 its reverse (33602015212), we get a palindrome (54853035845).

The spelling of 21251020633 in words is "twenty-one billion, two hundred fifty-one million, twenty thousand, six hundred thirty-three".