1661560690999 has 4 divisors (see below), whose sum is σ = 1812611662920. Its totient is φ = 1510509719080.

The previous prime is 1661560690987. The next prime is 1661560691057. The reversal of 1661560690999 is 9990960651661.

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

It is a cyclic number.

It is not a de Polignac number, because 1661560690999 - 2²⁵ = 1661527136567 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 (1661560690949) 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, 75525485944 + ... + 75525485965.

It is an arithmetic number, because the mean of its divisors is an integer number (453152915730).

Almost surely, 2^{1661560690999} is an apocalyptic number.

1661560690999 is a deficient number, since it is larger than the sum of its proper divisors (151050971921).

1661560690999 is a wasteful number, since it uses less digits than its factorization.

1661560690999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151050971920.

The product of its (nonzero) digits is 42515280, while the sum is 67.

The spelling of 1661560690999 in words is "one trillion, six hundred sixty-one billion, five hundred sixty million, six hundred ninety thousand, nine hundred ninety-nine".