21451433821 has 2 divisors, whose sum is σ = 21451433822. Its totient is φ = 21451433820.

The previous prime is 21451433803. The next prime is 21451433831. The reversal of 21451433821 is 12833415412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14960714596 + 6490719225 = 122314^2 + 80565^2 .

It is a cyclic number.

It is not a de Polignac number, because 21451433821 - 2¹⁷ = 21451302749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21451433831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725716910 + 10725716911.

It is an arithmetic number, because the mean of its divisors is an integer number (10725716911).

Almost surely, 2^21451433821 is an apocalyptic number.

It is an amenable number.

21451433821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451433821 is an equidigital number, since it uses as much as digits as its factorization.

21451433821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23040, while the sum is 34.

The spelling of 21451433821 in words is "twenty-one billion, four hundred fifty-one million, four hundred thirty-three thousand, eight hundred twenty-one".