21242450521 has 6 divisors (see below), whose sum is σ = 22565510030. Its totient is φ = 19992894336.

The previous prime is 21242450501. The next prime is 21242450549. The reversal of 21242450521 is 12505424212.

21242450521 = 8429² + 8430² + ... + 8717².

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 9935105625 + 11307344896 = 99675^2 + 106336^2 .

It is not a de Polignac number, because 21242450521 - 2¹³ = 21242442329 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21242450521.

It is not an unprimeable number, because it can be changed into a prime (21242450501) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36751356 + ... + 36751933.

Almost surely, 2^21242450521 is an apocalyptic number.

It is an amenable number.

21242450521 is a deficient number, since it is larger than the sum of its proper divisors (1323059509).

21242450521 is an equidigital number, since it uses as much as digits as its factorization.

21242450521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73503323 (or 73503306 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 28.

Adding to 21242450521 its reverse (12505424212), we get a palindrome (33747874733).

The spelling of 21242450521 in words is "twenty-one billion, two hundred forty-two million, four hundred fifty thousand, five hundred twenty-one".