1780001665 has 8 divisors (see below), whose sum is σ = 2300309928. Its totient is φ = 1314462720.

The previous prime is 1780001653. The next prime is 1780001687. The reversal of 1780001665 is 5661000871.

1780001665 = 5201² + 5202² + ... + 5265².

It can be written as a sum of positive squares in 4 ways, for example, as 52186176 + 1727815489 = 7224^2 + 41567^2 .

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

It is not a de Polignac number, because 1780001665 - 2¹⁹ = 1779477377 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1780001665.

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 7 ways as a sum of consecutive naturals, for example, 13692256 + ... + 13692385.

It is an arithmetic number, because the mean of its divisors is an integer number (287538741).

Almost surely, 2^1780001665 is an apocalyptic number.

It is an amenable number.

1780001665 is a deficient number, since it is larger than the sum of its proper divisors (520308263).

1780001665 is a wasteful number, since it uses less digits than its factorization.

1780001665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27384659.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 1780001665 is about 42190.0659515958. The cubic root of 1780001665 is about 1211.9186519793.

The spelling of 1780001665 in words is "one billion, seven hundred eighty million, one thousand, six hundred sixty-five".