816987890 has 16 divisors (see below), whose sum is σ = 1472842008. Its totient is φ = 326292096.

The previous prime is 816987877. The next prime is 816987893. The reversal of 816987890 is 98789618.

It is a happy number.

It is a Cunningham number, because it is equal to 28583²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 294088201 + 522899689 = 17149^2 + 22867^2 .

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (816987893) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 56027 + ... + 69086.

Almost surely, 2^816987890 is an apocalyptic number.

816987890 is a deficient number, since it is larger than the sum of its proper divisors (655854118).

816987890 is a wasteful number, since it uses less digits than its factorization.

816987890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125773.

The product of its (nonzero) digits is 1741824, while the sum is 56.

The square root of 816987890 is about 28583.0000174929. Note that the first 4 decimals coincide. The cubic root of 816987890 is about 934.8426970922.

The spelling of 816987890 in words is "eight hundred sixteen million, nine hundred eighty-seven thousand, eight hundred ninety".