61665821173 has 4 divisors (see below), whose sum is σ = 67271804928. Its totient is φ = 56059837420.

The previous prime is 61665821159. The next prime is 61665821177. The reversal of 61665821173 is 37112856616.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 61665821173 - 2³³ = 53075886581 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 (61665821177) 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, 2802991861 + ... + 2802991882.

It is an arithmetic number, because the mean of its divisors is an integer number (16817951232).

Almost surely, 2^61665821173 is an apocalyptic number.

It is an amenable number.

61665821173 is a deficient number, since it is larger than the sum of its proper divisors (5605983755).

61665821173 is a wasteful number, since it uses less digits than its factorization.

61665821173 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5605983754.

The product of its digits is 362880, while the sum is 46.

The spelling of 61665821173 in words is "sixty-one billion, six hundred sixty-five million, eight hundred twenty-one thousand, one hundred seventy-three".