61920209665 has 4 divisors (see below), whose sum is σ = 74304251604. Its totient is φ = 49536167728.

The previous prime is 61920209653. The next prime is 61920209707. The reversal of 61920209665 is 56690202916.

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 17787023424 + 44133186241 = 133368^2 + 210079^2 .

It is a cyclic number.

It is not a de Polignac number, because 61920209665 - 2⁷ = 61920209537 is a prime.

It is a super-2 number, since 2×61920209665² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6192020962 + ... + 6192020971.

It is an arithmetic number, because the mean of its divisors is an integer number (18576062901).

Almost surely, 2^61920209665 is an apocalyptic number.

It is an amenable number.

61920209665 is a deficient number, since it is larger than the sum of its proper divisors (12384041939).

61920209665 is a wasteful number, since it uses less digits than its factorization.

61920209665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12384041938.

The product of its (nonzero) digits is 349920, while the sum is 46.

The spelling of 61920209665 in words is "sixty-one billion, nine hundred twenty million, two hundred nine thousand, six hundred sixty-five".