61720649509 has 2 divisors, whose sum is σ = 61720649510. Its totient is φ = 61720649508.

The previous prime is 61720649491. The next prime is 61720649513. The reversal of 61720649509 is 90594602716.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61377585025 + 343064484 = 247745^2 + 18522^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61720649509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61720649539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30860324754 + 30860324755.

It is an arithmetic number, because the mean of its divisors is an integer number (30860324755).

Almost surely, 2^61720649509 is an apocalyptic number.

It is an amenable number.

61720649509 is a deficient number, since it is larger than the sum of its proper divisors (1).

61720649509 is an equidigital number, since it uses as much as digits as its factorization.

61720649509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 816480, while the sum is 49.

The spelling of 61720649509 in words is "sixty-one billion, seven hundred twenty million, six hundred forty-nine thousand, five hundred nine".