21030213521 has 2 divisors, whose sum is σ = 21030213522. Its totient is φ = 21030213520.

The previous prime is 21030213499. The next prime is 21030213559. The reversal of 21030213521 is 12531203012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19110021121 + 1920192400 = 138239^2 + 43820^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21030213521 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21030213493 and 21030213502.

It is not a weakly prime, because it can be changed into another prime (21030213221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515106760 + 10515106761.

It is an arithmetic number, because the mean of its divisors is an integer number (10515106761).

Almost surely, 2^21030213521 is an apocalyptic number.

It is an amenable number.

21030213521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21030213521 is an equidigital number, since it uses as much as digits as its factorization.

21030213521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 20.

Adding to 21030213521 its reverse (12531203012), we get a palindrome (33561416533).

The spelling of 21030213521 in words is "twenty-one billion, thirty million, two hundred thirteen thousand, five hundred twenty-one".