20871810 has 64 divisors (see below), whose sum is σ = 58095360. Its totient is φ = 5322240.

The previous prime is 20871769. The next prime is 20871853. The reversal of 20871810 is 1817802.

It is a super-2 number, since 2×20871810² = 871264905352200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 4530 + ... + 7890.

It is an arithmetic number, because the mean of its divisors is an integer number (907740).

Almost surely, 2^20871810 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20871810, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29047680).

20871810 is an abundant number, since it is smaller than the sum of its proper divisors (37223550).

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

20871810 is a wasteful number, since it uses less digits than its factorization.

20871810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3400 (or 3394 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 20871810 is about 4568.5676092185. The cubic root of 20871810 is about 275.3298961021.

The spelling of 20871810 in words is "twenty million, eight hundred seventy-one thousand, eight hundred ten".