21029384821 has 2 divisors, whose sum is σ = 21029384822. Its totient is φ = 21029384820.

The previous prime is 21029384777. The next prime is 21029384837. The reversal of 21029384821 is 12848392012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21029350225 + 34596 = 145015^2 + 186^2 .

It is a cyclic number.

It is not a de Polignac number, because 21029384821 - 2⁹ = 21029384309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21029384881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10514692410 + 10514692411.

It is an arithmetic number, because the mean of its divisors is an integer number (10514692411).

Almost surely, 2^21029384821 is an apocalyptic number.

It is an amenable number.

21029384821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21029384821 is an equidigital number, since it uses as much as digits as its factorization.

21029384821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 55296, while the sum is 40.

The spelling of 21029384821 in words is "twenty-one billion, twenty-nine million, three hundred eighty-four thousand, eight hundred twenty-one".