1861216985 has 4 divisors (see below), whose sum is σ = 2233460388. Its totient is φ = 1488973584.

The previous prime is 1861216949. The next prime is 1861216997. The reversal of 1861216985 is 5896121681.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5896121681 = 36037 ⋅163613.

It can be written as a sum of positive squares in 2 ways, for example, as 416608921 + 1444608064 = 20411^2 + 38008^2 .

It is a cyclic number.

It is not a de Polignac number, because 1861216985 - 2⁶ = 1861216921 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 186121694 + ... + 186121703.

It is an arithmetic number, because the mean of its divisors is an integer number (558365097).

Almost surely, 2^1861216985 is an apocalyptic number.

It is an amenable number.

1861216985 is a deficient number, since it is larger than the sum of its proper divisors (372243403).

1861216985 is an equidigital number, since it uses as much as digits as its factorization.

1861216985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372243402.

The product of its digits is 207360, while the sum is 47.

The square root of 1861216985 is about 43141.8240805833. The cubic root of 1861216985 is about 1230.0771064536.

The spelling of 1861216985 in words is "one billion, eight hundred sixty-one million, two hundred sixteen thousand, nine hundred eighty-five".