820561457 has 6 divisors (see below), whose sum is σ = 871669398. Its totient is φ = 772292864.

The previous prime is 820561433. The next prime is 820561463. The reversal of 820561457 is 754165028.

It can be written as a sum of positive squares in 3 ways, for example, as 345365056 + 475196401 = 18584^2 + 21799^2 .

It is not a de Polignac number, because 820561457 - 2⁸ = 820561201 is a prime.

It is a super-2 number, since 2×820561457² = 1346642209427925698, which contains 22 as substring.

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 820561457.

It is not an unprimeable number, because it can be changed into a prime (820561477) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1419368 + ... + 1419945.

It is an arithmetic number, because the mean of its divisors is an integer number (145278233).

Almost surely, 2^820561457 is an apocalyptic number.

It is an amenable number.

820561457 is a deficient number, since it is larger than the sum of its proper divisors (51107941).

820561457 is a wasteful number, since it uses less digits than its factorization.

820561457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2839347 (or 2839330 counting only the distinct ones).

The product of its (nonzero) digits is 67200, while the sum is 38.

The square root of 820561457 is about 28645.4439134743. The cubic root of 820561457 is about 936.2037388721.

The spelling of 820561457 in words is "eight hundred twenty million, five hundred sixty-one thousand, four hundred fifty-seven".