816987889 has 9 divisors (see below), whose sum is σ = 828083019. Its totient is φ = 806040600.

The previous prime is 816987877. The next prime is 816987893. The reversal of 816987889 is 988789618.

The square root of 816987889 is 28583.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 784952289 + 32035600 = 28017^2 + 5660^2 .

It is not a de Polignac number, because 816987889 - 2²¹ = 814890737 is a prime.

It is a Duffinian number.

Its product of digits (13934592) is a multiple of the sum of its prime divisors (384).

It is a self number, because there is not a number n which added to its sum of digits gives 816987889.

It is not an unprimeable number, because it can be changed into a prime (816987869) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2886742 + ... + 2887024.

Almost surely, 2^816987889 is an apocalyptic number.

816987889 is the 28583-rd square number.

816987889 is the 14292-nd centered octagonal number.

It is an amenable number.

816987889 is a deficient number, since it is larger than the sum of its proper divisors (11095130).

816987889 is an frugal number, since it uses more digits than its factorization.

816987889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 768 (or 384 counting only the distinct ones).

The product of its digits is 13934592, while the sum is 64.

The cubic root of 816987889 is about 934.8426967108.

Multiplying 816987889 by its sum of digits (64), we get a square (52287224896 = 228664²).

The spelling of 816987889 in words is "eight hundred sixteen million, nine hundred eighty-seven thousand, eight hundred eighty-nine".