21259932821 has 2 divisors, whose sum is σ = 21259932822. Its totient is φ = 21259932820.

The previous prime is 21259932791. The next prime is 21259932833. The reversal of 21259932821 is 12823995212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20894702500 + 365230321 = 144550^2 + 19111^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21259932821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21259932521) 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, 10629966410 + 10629966411.

It is an arithmetic number, because the mean of its divisors is an integer number (10629966411).

Almost surely, 2^21259932821 is an apocalyptic number.

It is an amenable number.

21259932821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21259932821 is an equidigital number, since it uses as much as digits as its factorization.

21259932821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 155520, while the sum is 44.

The spelling of 21259932821 in words is "twenty-one billion, two hundred fifty-nine million, nine hundred thirty-two thousand, eight hundred twenty-one".