20871765 has 24 divisors (see below), whose sum is σ = 36293400. Its totient is φ = 11096064.

The previous prime is 20871757. The next prime is 20871769. The reversal of 20871765 is 56717802.

It can be written as a sum of positive squares in 4 ways, for example, as 8191044 + 12680721 = 2862^2 + 3561^2 .

It is not a de Polignac number, because 20871765 - 2³ = 20871757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20871769) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19689 + ... + 20721.

It is an arithmetic number, because the mean of its divisors is an integer number (1512225).

Almost surely, 2^20871765 is an apocalyptic number.

It is an amenable number.

20871765 is a deficient number, since it is larger than the sum of its proper divisors (15421635).

20871765 is a wasteful number, since it uses less digits than its factorization.

20871765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1493 (or 1490 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 20871765 is about 4568.5626842586. The cubic root of 20871765 is about 275.3296982299.

The spelling of 20871765 in words is "twenty million, eight hundred seventy-one thousand, seven hundred sixty-five".