20931280 has 20 divisors (see below), whose sum is σ = 48665412. Its totient is φ = 8372480.

The previous prime is 20931263. The next prime is 20931289. The reversal of 20931280 is 8213902.

It can be written as a sum of positive squares in 2 ways, for example, as 12027024 + 8904256 = 3468^2 + 2984^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20931289) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 130741 + ... + 130900.

Almost surely, 2^20931280 is an apocalyptic number.

20931280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20931280 is an abundant number, since it is smaller than the sum of its proper divisors (27734132).

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

20931280 is a wasteful number, since it uses less digits than its factorization.

20931280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261654 (or 261648 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20931280 is about 4575.0715841394. The cubic root of 20931280 is about 275.5911470773.

The spelling of 20931280 in words is "twenty million, nine hundred thirty-one thousand, two hundred eighty".