1661890001 has 6 divisors (see below), whose sum is σ = 1737288210. Its totient is φ = 1589633408.

The previous prime is 1661889991. The next prime is 1661890033. The reversal of 1661890001 is 1000981661.

It can be written as a sum of positive squares in only one way, i.e., 1036840000 + 625050001 = 32200^2 + 25001^2 .

It is not a de Polignac number, because 1661890001 - 2¹⁴ = 1661873617 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661890001.

It is not an unprimeable number, because it can be changed into a prime (1661890051) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1570256 + ... + 1571313.

It is an arithmetic number, because the mean of its divisors is an integer number (289548035).

Almost surely, 2^1661890001 is an apocalyptic number.

It is an amenable number.

1661890001 is a deficient number, since it is larger than the sum of its proper divisors (75398209).

1661890001 is an equidigital number, since it uses as much as digits as its factorization.

1661890001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3141615 (or 3141592 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 1661890001 is about 40766.2851017848. The cubic root of 1661890001 is about 1184.4973450156.

The spelling of 1661890001 in words is "one billion, six hundred sixty-one million, eight hundred ninety thousand, one".