1661555556597 has 48 divisors (see below), whose sum is σ = 2396299771008. Its totient is φ = 1022106624000.

The previous prime is 1661555556581. The next prime is 1661555556599. The reversal of 1661555556597 is 7956555551661.

It is not a de Polignac number, because 1661555556597 - 2⁴ = 1661555556581 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661555556599) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 69216597 + ... + 69240597.

It is an arithmetic number, because the mean of its divisors is an integer number (49922911896).

Almost surely, 2^{1661555556597} is an apocalyptic number.

It is an amenable number.

1661555556597 is a deficient number, since it is larger than the sum of its proper divisors (734744214411).

1661555556597 is a wasteful number, since it uses less digits than its factorization.

1661555556597 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25278 (or 25249 counting only the distinct ones).

The product of its digits is 212625000, while the sum is 66.

The spelling of 1661555556597 in words is "one trillion, six hundred sixty-one billion, five hundred fifty-five million, five hundred fifty-six thousand, five hundred ninety-seven".