821694661443 has 8 divisors (see below), whose sum is σ = 1217325424400. Its totient is φ = 547796440944.

The previous prime is 821694661429. The next prime is 821694661453. The reversal of 821694661443 is 344166496128.

821694661443 is a `hidden beast` number, since 8 + 2 + 16 + 9 + 4 + 6 + 614 + 4 + 3 = 666.

It is not a de Polignac number, because 821694661443 - 2³⁴ = 804514792259 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 821694661443.

It is not an unprimeable number, because it can be changed into a prime (821694661423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15216567778 + ... + 15216567831.

It is an arithmetic number, because the mean of its divisors is an integer number (152165678050).

Almost surely, 2^821694661443 is an apocalyptic number.

821694661443 is a deficient number, since it is larger than the sum of its proper divisors (395630762957).

821694661443 is a wasteful number, since it uses less digits than its factorization.

821694661443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30433135618 (or 30433135612 counting only the distinct ones).

The product of its digits is 5971968, while the sum is 54.

The spelling of 821694661443 in words is "eight hundred twenty-one billion, six hundred ninety-four million, six hundred sixty-one thousand, four hundred forty-three".