1661999709 has 8 divisors (see below), whose sum is σ = 2244050560. Its totient is φ = 1093974336.

The previous prime is 1661999699. The next prime is 1661999741. The reversal of 1661999709 is 9079991661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1661999709 - 2¹⁵ = 1661966941 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 (1661999909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3506092 + ... + 3506565.

It is an arithmetic number, because the mean of its divisors is an integer number (280506320).

Almost surely, 2^1661999709 is an apocalyptic number.

It is an amenable number.

1661999709 is a deficient number, since it is larger than the sum of its proper divisors (582050851).

1661999709 is an equidigital number, since it uses as much as digits as its factorization.

1661999709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7012739.

The product of its (nonzero) digits is 1653372, while the sum is 57.

The square root of 1661999709 is about 40767.6306522712. The cubic root of 1661999709 is about 1184.5234089097.

The spelling of 1661999709 in words is "one billion, six hundred sixty-one million, nine hundred ninety-nine thousand, seven hundred nine".