816806661 has 16 divisors (see below), whose sum is σ = 1189106688. Its totient is φ = 494607600.

The previous prime is 816806621. The next prime is 816806671. The reversal of 816806661 is 166608618.

It is not a de Polignac number, because 816806661 - 2⁷ = 816806533 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816806621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30570 + ... + 50676.

It is an arithmetic number, because the mean of its divisors is an integer number (74319168).

Almost surely, 2^816806661 is an apocalyptic number.

It is an amenable number.

816806661 is a deficient number, since it is larger than the sum of its proper divisors (372300027).

816806661 is a wasteful number, since it uses less digits than its factorization.

816806661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21352.

The product of its (nonzero) digits is 82944, while the sum is 42.

The square root of 816806661 is about 28579.8296181065. The cubic root of 816806661 is about 934.7735679011.

The spelling of 816806661 in words is "eight hundred sixteen million, eight hundred six thousand, six hundred sixty-one".