61349840721 has 135 divisors (see below), whose sum is σ = 104205245859. Its totient is φ = 35952553728.

The previous prime is 61349840719. The next prime is 61349840749. The reversal of 61349840721 is 12704894316.

The square root of 61349840721 is 247689.

It is a perfect power (a square), and thus also a powerful number.

61349840721 is a `hidden beast` number, since 6 + 134 + 98 + 407 + 21 = 666.

It can be written as a sum of positive squares in 13 ways, for example, as 47912394321 + 13437446400 = 218889^2 + 115920^2 .

It is not a de Polignac number, because 61349840721 - 2¹ = 61349840719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (61349840701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 840408741 + ... + 840408813.

Almost surely, 2^61349840721 is an apocalyptic number.

61349840721 is the 247689-th square number.

61349840721 is the 123845-th centered octagonal number.

It is an amenable number.

61349840721 is a deficient number, since it is larger than the sum of its proper divisors (42855405138).

61349840721 is an equidigital number, since it uses as much as digits as its factorization.

61349840721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 118 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 61349840721 in words is "sixty-one billion, three hundred forty-nine million, eight hundred forty thousand, seven hundred twenty-one".