820647891 has 48 divisors (see below), whose sum is σ = 1380907008. Its totient is φ = 459950400.

The previous prime is 820647869. The next prime is 820647899. The reversal of 820647891 is 198746028.

It is not a de Polignac number, because 820647891 - 2¹⁰ = 820646867 is a prime.

It is a super-2 number, since 2×820647891² = 1346925922005495762, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (820647899) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1211845 + ... + 1212521.

It is an arithmetic number, because the mean of its divisors is an integer number (28768896).

Almost surely, 2^820647891 is an apocalyptic number.

820647891 is a deficient number, since it is larger than the sum of its proper divisors (560259117).

820647891 is a wasteful number, since it uses less digits than its factorization.

820647891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1032 (or 1029 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 45.

The square root of 820647891 is about 28646.9525604383. The cubic root of 820647891 is about 936.2366094521.

The spelling of 820647891 in words is "eight hundred twenty million, six hundred forty-seven thousand, eight hundred ninety-one".