63537840721 has 2 divisors, whose sum is σ = 63537840722. Its totient is φ = 63537840720.

The previous prime is 63537840719. The next prime is 63537840781. The reversal of 63537840721 is 12704873536.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 45843520321 + 17694320400 = 214111^2 + 133020^2 .

It is a cyclic number.

It is not a de Polignac number, because 63537840721 - 2¹ = 63537840719 is a prime.

Together with 63537840719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (63537840781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31768920360 + 31768920361.

It is an arithmetic number, because the mean of its divisors is an integer number (31768920361).

Almost surely, 2^63537840721 is an apocalyptic number.

It is an amenable number.

63537840721 is a deficient number, since it is larger than the sum of its proper divisors (1).

63537840721 is an equidigital number, since it uses as much as digits as its factorization.

63537840721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 846720, while the sum is 46.

The spelling of 63537840721 in words is "sixty-three billion, five hundred thirty-seven million, eight hundred forty thousand, seven hundred twenty-one".