20865780 has 144 divisors (see below), whose sum is σ = 70294224. Its totient is φ = 4976640.

The previous prime is 20865773. The next prime is 20865797. The reversal of 20865780 is 8756802.

20865780 is a `hidden beast` number, since 2 + 0 + 86 + 578 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 181476 + 20684304 = 426^2 + 4548^2 .

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 86460 + ... + 86700.

Almost surely, 2^20865780 is an apocalyptic number.

20865780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20865780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35147112).

20865780 is an abundant number, since it is smaller than the sum of its proper divisors (49428444).

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

20865780 is a wasteful number, since it uses less digits than its factorization.

20865780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306 (or 301 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 20865780 is about 4567.9076172795. The cubic root of 20865780 is about 275.3033786896.

The spelling of 20865780 in words is "twenty million, eight hundred sixty-five thousand, seven hundred eighty".