20730840 has 128 divisors (see below), whose sum is σ = 68160960. Its totient is φ = 5013504.

The previous prime is 20730839. The next prime is 20730869. The reversal of 20730840 is 4803702.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 20730840.

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, 151252 + ... + 151388.

Almost surely, 2^20730840 is an apocalyptic number.

20730840 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 20730840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34080480).

20730840 is an abundant number, since it is smaller than the sum of its proper divisors (47430120).

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

20730840 is a wasteful number, since it uses less digits than its factorization.

20730840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261 (or 257 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 24.

The square root of 20730840 is about 4553.1132206437. The cubic root of 20730840 is about 274.7086280295.

The spelling of 20730840 in words is "twenty million, seven hundred thirty thousand, eight hundred forty".