1661999515 has 16 divisors (see below), whose sum is σ = 2179457280. Its totient is φ = 1206644320.

The previous prime is 1661999513. The next prime is 1661999539. The reversal of 1661999515 is 5159991661.

It is a happy number.

It is not a de Polignac number, because 1661999515 - 2¹ = 1661999513 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1661999513) 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 15 ways as a sum of consecutive naturals, for example, 6546 + ... + 58024.

It is an arithmetic number, because the mean of its divisors is an integer number (136216080).

Almost surely, 2^1661999515 is an apocalyptic number.

1661999515 is a deficient number, since it is larger than the sum of its proper divisors (517457765).

1661999515 is a wasteful number, since it uses less digits than its factorization.

1661999515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52082.

The product of its digits is 656100, while the sum is 52.

The square root of 1661999515 is about 40767.6282729324. The cubic root of 1661999515 is about 1184.5233628212.

The spelling of 1661999515 in words is "one billion, six hundred sixty-one million, nine hundred ninety-nine thousand, five hundred fifteen".