21530266013 has 4 divisors (see below), whose sum is σ = 21548016828. Its totient is φ = 21512515200.

The previous prime is 21530266007. The next prime is 21530266019. The reversal of 21530266013 is 31066203512.

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

It is an interprime number because it is at equal distance from previous prime (21530266007) and next prime (21530266019).

It can be written as a sum of positive squares in 2 ways, for example, as 3051126169 + 18479139844 = 55237^2 + 135938^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21530266013 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530266019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8873588 + ... + 8876013.

It is an arithmetic number, because the mean of its divisors is an integer number (5387004207).

Almost surely, 2^21530266013 is an apocalyptic number.

It is an amenable number.

21530266013 is a deficient number, since it is larger than the sum of its proper divisors (17750815).

21530266013 is a wasteful number, since it uses less digits than its factorization.

21530266013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17750814.

The product of its (nonzero) digits is 6480, while the sum is 29.

Adding to 21530266013 its reverse (31066203512), we get a palindrome (52596469525).

The spelling of 21530266013 in words is "twenty-one billion, five hundred thirty million, two hundred sixty-six thousand, thirteen".