61720717165 has 4 divisors (see below), whose sum is σ = 74064860604. Its totient is φ = 49376573728.

The previous prime is 61720717073. The next prime is 61720717169. The reversal of 61720717165 is 56171702716.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 27168599241 + 34552117924 = 164829^2 + 185882^2 .

It is a cyclic number.

It is not a de Polignac number, because 61720717165 - 2²¹ = 61718620013 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61720717169) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6172071712 + ... + 6172071721.

It is an arithmetic number, because the mean of its divisors is an integer number (18516215151).

Almost surely, 2^61720717165 is an apocalyptic number.

It is an amenable number.

61720717165 is a deficient number, since it is larger than the sum of its proper divisors (12344143439).

61720717165 is a wasteful number, since it uses less digits than its factorization.

61720717165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12344143438.

The product of its (nonzero) digits is 123480, while the sum is 43.

The spelling of 61720717165 in words is "sixty-one billion, seven hundred twenty million, seven hundred seventeen thousand, one hundred sixty-five".