21035443721 has 2 divisors, whose sum is σ = 21035443722. Its totient is φ = 21035443720.

The previous prime is 21035443717. The next prime is 21035443733. The reversal of 21035443721 is 12734453012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19667257600 + 1368186121 = 140240^2 + 36989^2 .

It is a cyclic number.

It is not a de Polignac number, because 21035443721 - 2² = 21035443717 is a prime.

It is not a weakly prime, because it can be changed into another prime (21035443771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10517721860 + 10517721861.

It is an arithmetic number, because the mean of its divisors is an integer number (10517721861).

Almost surely, 2^21035443721 is an apocalyptic number.

It is an amenable number.

21035443721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21035443721 is an equidigital number, since it uses as much as digits as its factorization.

21035443721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 32.

Adding to 21035443721 its reverse (12734453012), we get a palindrome (33769896733).

The spelling of 21035443721 in words is "twenty-one billion, thirty-five million, four hundred forty-three thousand, seven hundred twenty-one".