1871287821 has 18 divisors (see below), whose sum is σ = 2926888458. Its totient is φ = 1151560800.

The previous prime is 1871287799. The next prime is 1871287841. The reversal of 1871287821 is 1287821781.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 122877225 + 1748410596 = 11085^2 + 41814^2 .

It is not a de Polignac number, because 1871287821 - 2⁶ = 1871287757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1871287841) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 613630 + ... + 616671.

Almost surely, 2^1871287821 is an apocalyptic number.

It is an amenable number.

1871287821 is a deficient number, since it is larger than the sum of its proper divisors (1055600637).

1871287821 is a wasteful number, since it uses less digits than its factorization.

1871287821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1230333 (or 1230317 counting only the distinct ones).

The product of its digits is 100352, while the sum is 45.

The square root of 1871287821 is about 43258.3844011771. The cubic root of 1871287821 is about 1232.2917199104.

The spelling of 1871287821 in words is "one billion, eight hundred seventy-one million, two hundred eighty-seven thousand, eight hundred twenty-one".