861891020 has 24 divisors (see below), whose sum is σ = 1872385200. Its totient is φ = 332868032.

The previous prime is 861891001. The next prime is 861891031. The reversal of 861891020 is 20198168.

It is a super-2 number, since 2×861891020² = 1485712260713280800, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 742430 + ... + 743589.

It is an arithmetic number, because the mean of its divisors is an integer number (78016050).

Almost surely, 2^861891020 is an apocalyptic number.

It is an amenable number.

861891020 is an abundant number, since it is smaller than the sum of its proper divisors (1010494180).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

861891020 is a wasteful number, since it uses less digits than its factorization.

861891020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1486057 (or 1486055 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 861891020 is about 29357.9805163775. The cubic root of 861891020 is about 951.6650467586.

The spelling of 861891020 in words is "eight hundred sixty-one million, eight hundred ninety-one thousand, twenty".