1909998985 has 4 divisors (see below), whose sum is σ = 2291998788. Its totient is φ = 1527999184.

The previous prime is 1909998973. The next prime is 1909998989. The reversal of 1909998985 is 5898999091.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5898999091 = 66851 ⋅88241.

It can be written as a sum of positive squares in 2 ways, for example, as 844890489 + 1065108496 = 29067^2 + 32636^2 .

It is a cyclic number.

It is not a de Polignac number, because 1909998985 - 2⁵ = 1909998953 is a prime.

It is a super-2 number, since 2×1909998985² = 7296192245402060450, which contains 22 as substring.

It is a Smith number, since the sum of its digits (67) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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 1909998985.

It is not an unprimeable number, because it can be changed into a prime (1909998989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 190999894 + ... + 190999903.

It is an arithmetic number, because the mean of its divisors is an integer number (572999697).

Almost surely, 2^1909998985 is an apocalyptic number.

It is an amenable number.

1909998985 is a deficient number, since it is larger than the sum of its proper divisors (381999803).

1909998985 is an equidigital number, since it uses as much as digits as its factorization.

1909998985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 381999802.

The product of its (nonzero) digits is 18895680, while the sum is 67.

The square root of 1909998985 is about 43703.5351544929. The cubic root of 1909998985 is about 1240.7312251910.

The spelling of 1909998985 in words is "one billion, nine hundred nine million, nine hundred ninety-eight thousand, nine hundred eighty-five".