20861840 has 20 divisors (see below), whose sum is σ = 48503964. Its totient is φ = 8344704.

The previous prime is 20861833. The next prime is 20861891. The reversal of 20861840 is 4816802.

It can be written as a sum of positive squares in 2 ways, for example, as 12475024 + 8386816 = 3532^2 + 2896^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 130307 + ... + 130466.

Almost surely, 2^20861840 is an apocalyptic number.

20861840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20861840 is an abundant number, since it is smaller than the sum of its proper divisors (27642124).

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

20861840 is a wasteful number, since it uses less digits than its factorization.

20861840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260786 (or 260780 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 20861840 is about 4567.4763272512. The cubic root of 20861840 is about 275.2860494614.

The spelling of 20861840 in words is "twenty million, eight hundred sixty-one thousand, eight hundred forty".