819910661 has 8 divisors (see below), whose sum is σ = 867003648. Its totient is φ = 774108000.

The previous prime is 819910643. The next prime is 819910681. The reversal of 819910661 is 166019918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 819910661 - 2¹⁸ = 819648517 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (819910621) 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, 321275 + ... + 323816.

It is an arithmetic number, because the mean of its divisors is an integer number (108375456).

Almost surely, 2^819910661 is an apocalyptic number.

It is an amenable number.

819910661 is a deficient number, since it is larger than the sum of its proper divisors (47092987).

819910661 is a wasteful number, since it uses less digits than its factorization.

819910661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645163.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 819910661 is about 28634.0821574570. The cubic root of 819910661 is about 935.9561690368.

The spelling of 819910661 in words is "eight hundred nineteen million, nine hundred ten thousand, six hundred sixty-one".