20391680 has 72 divisors (see below), whose sum is σ = 49669200. Its totient is φ = 8019968.

The previous prime is 20391677. The next prime is 20391713. The reversal of 20391680 is 8619302.

It is a super-2 number, since 2×20391680² = 831641226444800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 113831 + ... + 114009.

It is an arithmetic number, because the mean of its divisors is an integer number (689850).

Almost surely, 2^20391680 is an apocalyptic number.

20391680 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 20391680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24834600).

20391680 is an abundant number, since it is smaller than the sum of its proper divisors (29277520).

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

20391680 is an equidigital number, since it uses as much as digits as its factorization.

20391680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289 (or 275 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 20391680 is about 4515.7147828445. The cubic root of 20391680 is about 273.2022902813.

The spelling of 20391680 in words is "twenty million, three hundred ninety-one thousand, six hundred eighty".