61665606591 has 16 divisors (see below), whose sum is σ = 87954832224. Its totient is φ = 38293254144.

The previous prime is 61665606571. The next prime is 61665606593. The reversal of 61665606591 is 19560656616.

It is a happy number.

It is not a de Polignac number, because 61665606591 - 2²⁵ = 61632052159 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61665606593) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6227680 + ... + 6237573.

It is an arithmetic number, because the mean of its divisors is an integer number (5497177014).

Almost surely, 2^61665606591 is an apocalyptic number.

61665606591 is a deficient number, since it is larger than the sum of its proper divisors (26289225633).

61665606591 is a wasteful number, since it uses less digits than its factorization.

61665606591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12465370.

The product of its (nonzero) digits is 1749600, while the sum is 51.

The spelling of 61665606591 in words is "sixty-one billion, six hundred sixty-five million, six hundred six thousand, five hundred ninety-one".