20871640 has 16 divisors (see below), whose sum is σ = 46961280. Its totient is φ = 8348640.

The previous prime is 20871637. The next prime is 20871659. The reversal of 20871640 is 4617802.

It is a junction number, because it is equal to n+sod(n) for n = 20871599 and 20871608.

It is a congruent number.

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, 260856 + ... + 260935.

It is an arithmetic number, because the mean of its divisors is an integer number (2935080).

Almost surely, 2^20871640 is an apocalyptic number.

20871640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20871640 is an abundant number, since it is smaller than the sum of its proper divisors (26089640).

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

20871640 is a wasteful number, since it uses less digits than its factorization.

20871640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521802 (or 521798 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 20871640 is about 4568.5490037867. The cubic root of 20871640 is about 275.3291485833.

The spelling of 20871640 in words is "twenty million, eight hundred seventy-one thousand, six hundred forty".