21080780 has 60 divisors (see below), whose sum is σ = 51762480. Its totient is φ = 7211232.

The previous prime is 21080777. The next prime is 21080789. The reversal of 21080780 is 8708012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21080789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 47801 + ... + 48239.

It is an arithmetic number, because the mean of its divisors is an integer number (862708).

Almost surely, 2^21080780 is an apocalyptic number.

21080780 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 21080780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25881240).

21080780 is an abundant number, since it is smaller than the sum of its proper divisors (30681700).

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

21080780 is an equidigital number, since it uses as much as digits as its factorization.

21080780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 476 (or 453 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 26.

The square root of 21080780 is about 4591.3810558480. The cubic root of 21080780 is about 276.2457204008.

Adding to 21080780 its reverse (8708012), we get a palindrome (29788792).

The spelling of 21080780 in words is "twenty-one million, eighty thousand, seven hundred eighty".