20649780 has 72 divisors (see below), whose sum is σ = 63390600. Its totient is φ = 5440512.

The previous prime is 20649767. The next prime is 20649803. The reversal of 20649780 is 8794602.

20649780 is a `hidden beast` number, since 2 + 0 + 649 + 7 + 8 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2090916 + 18558864 = 1446^2 + 4308^2 .

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 pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15376 + ... + 16664.

It is an arithmetic number, because the mean of its divisors is an integer number (880425).

Almost surely, 2^20649780 is an apocalyptic number.

20649780 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 20649780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31695300).

20649780 is an abundant number, since it is smaller than the sum of its proper divisors (42740820).

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

20649780 is a wasteful number, since it uses less digits than its factorization.

20649780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1393 (or 1388 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 20649780 is about 4544.2029003996. The cubic root of 20649780 is about 274.3501127621.

The spelling of 20649780 in words is "twenty million, six hundred forty-nine thousand, seven hundred eighty".