21621240013 has 2 divisors, whose sum is σ = 21621240014. Its totient is φ = 21621240012.

The previous prime is 21621240007. The next prime is 21621240037. The reversal of 21621240013 is 31004212612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21258223204 + 363016809 = 145802^2 + 19053^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21621240013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21621240313) 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 as a sum of consecutive naturals, namely, 10810620006 + 10810620007.

It is an arithmetic number, because the mean of its divisors is an integer number (10810620007).

Almost surely, 2^21621240013 is an apocalyptic number.

It is an amenable number.

21621240013 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621240013 is an equidigital number, since it uses as much as digits as its factorization.

21621240013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 22.

Adding to 21621240013 its reverse (31004212612), we get a palindrome (52625452625).

The spelling of 21621240013 in words is "twenty-one billion, six hundred twenty-one million, two hundred forty thousand, thirteen".