816873561 has 27 divisors (see below), whose sum is σ = 1373579103. Its totient is φ = 466441920.

The previous prime is 816873553. The next prime is 816873571. The reversal of 816873561 is 165378618.

The square root of 816873561 is 28581.

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

816873561 is a `hidden beast` number, since 8 + 1 + 6 + 87 + 3 + 561 = 666.

It can be written as a sum of positive squares in only one way, i.e., 138791961 + 678081600 = 11781^2 + 26040^2 .

It is not a de Polignac number, because 816873561 - 2³ = 816873553 is a prime.

It is not an unprimeable number, because it can be changed into a prime (816873521) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 599521 + ... + 600881.

Almost surely, 2^816873561 is an apocalyptic number.

816873561 is the 28581-st square number.

816873561 is the 14291-st centered octagonal number.

It is an amenable number.

816873561 is a deficient number, since it is larger than the sum of its proper divisors (556705542).

816873561 is an equidigital number, since it uses as much as digits as its factorization.

816873561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2742 (or 1371 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The cubic root of 816873561 is about 934.7990878711.

The spelling of 816873561 in words is "eight hundred sixteen million, eight hundred seventy-three thousand, five hundred sixty-one".