820811656493 has 4 divisors (see below), whose sum is σ = 821579488860. Its totient is φ = 820043824128.

The previous prime is 820811656403. The next prime is 820811656499. The reversal of 820811656493 is 394656118028.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 261671125444 + 559140531049 = 511538^2 + 747757^2 .

It is a cyclic number.

It is not a de Polignac number, because 820811656493 - 2¹⁴ = 820811640109 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820811656499) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 383914580 + ... + 383916717.

It is an arithmetic number, because the mean of its divisors is an integer number (205394872215).

Almost surely, 2^820811656493 is an apocalyptic number.

It is an amenable number.

820811656493 is a deficient number, since it is larger than the sum of its proper divisors (767832367).

820811656493 is a wasteful number, since it uses less digits than its factorization.

820811656493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 767832366.

The product of its (nonzero) digits is 2488320, while the sum is 53.

The spelling of 820811656493 in words is "eight hundred twenty billion, eight hundred eleven million, six hundred fifty-six thousand, four hundred ninety-three".