1871198821 has 4 divisors (see below), whose sum is σ = 1889725644. Its totient is φ = 1852672000.

The previous prime is 1871198809. The next prime is 1871198863. The reversal of 1871198821 is 1288911781.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1288911781 = 79 ⋅16315339.

It can be written as a sum of positive squares in 2 ways, for example, as 1456261921 + 414936900 = 38161^2 + 20370^2 .

It is a cyclic number.

It is not a de Polignac number, because 1871198821 - 2¹¹ = 1871196773 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1871198321) 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, 9263260 + ... + 9263461.

It is an arithmetic number, because the mean of its divisors is an integer number (472431411).

Almost surely, 2^1871198821 is an apocalyptic number.

It is an amenable number.

1871198821 is a deficient number, since it is larger than the sum of its proper divisors (18526823).

1871198821 is a wasteful number, since it uses less digits than its factorization.

1871198821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18526822.

The product of its digits is 64512, while the sum is 46.

The square root of 1871198821 is about 43257.3556866344. The cubic root of 1871198821 is about 1232.2721833287.

The spelling of 1871198821 in words is "one billion, eight hundred seventy-one million, one hundred ninety-eight thousand, eight hundred twenty-one".