820644774436 has 12 divisors (see below), whose sum is σ = 1436402828812. Its totient is φ = 410243966208.

The previous prime is 820644774431. The next prime is 820644774451. The reversal of 820644774436 is 634477446028.

It can be written as a sum of positive squares in 2 ways, for example, as 434009534436 + 386635240000 = 658794^2 + 621800^2 .

It is a super-2 number, since 2×820644774436² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (820644774431) 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, 19581705 + ... + 19623568.

Almost surely, 2^820644774436 is an apocalyptic number.

It is an amenable number.

820644774436 is a deficient number, since it is larger than the sum of its proper divisors (615758054376).

820644774436 is a wasteful number, since it uses less digits than its factorization.

820644774436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39210510 (or 39210508 counting only the distinct ones).

The product of its (nonzero) digits is 21676032, while the sum is 55.

The spelling of 820644774436 in words is "eight hundred twenty billion, six hundred forty-four million, seven hundred seventy-four thousand, four hundred thirty-six".