21700347521 has 2 divisors, whose sum is σ = 21700347522. Its totient is φ = 21700347520.

The previous prime is 21700347517. The next prime is 21700347577. The reversal of 21700347521 is 12574300712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21582841921 + 117505600 = 146911^2 + 10840^2 .

It is a cyclic number.

It is not a de Polignac number, because 21700347521 - 2² = 21700347517 is a prime.

It is not a weakly prime, because it can be changed into another prime (21700347511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850173760 + 10850173761.

It is an arithmetic number, because the mean of its divisors is an integer number (10850173761).

Almost surely, 2^21700347521 is an apocalyptic number.

It is an amenable number.

21700347521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21700347521 is an equidigital number, since it uses as much as digits as its factorization.

21700347521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11760, while the sum is 32.

The spelling of 21700347521 in words is "twenty-one billion, seven hundred million, three hundred forty-seven thousand, five hundred twenty-one".