1661071665 has 24 divisors (see below), whose sum is σ = 2921292864. Its totient is φ = 805367200.

The previous prime is 1661071651. The next prime is 1661071681. The reversal of 1661071665 is 5661701661.

It is not a de Polignac number, because 1661071665 - 2⁷ = 1661071537 is a prime.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 455781 + ... + 459410.

It is an arithmetic number, because the mean of its divisors is an integer number (121720536).

Almost surely, 2^1661071665 is an apocalyptic number.

1661071665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661071665 is a deficient number, since it is larger than the sum of its proper divisors (1260221199).

1661071665 is a wasteful number, since it uses less digits than its factorization.

1661071665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 915221 (or 915210 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 39.

The square root of 1661071665 is about 40756.2469444869. The cubic root of 1661071665 is about 1184.3028925220.

The spelling of 1661071665 in words is "one billion, six hundred sixty-one million, seventy-one thousand, six hundred sixty-five".