21043780 has 48 divisors (see below), whose sum is σ = 45997056. Its totient is φ = 8081280.

The previous prime is 21043753. The next prime is 21043793. The reversal of 21043780 is 8734012.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57157 + ... + 57523.

It is an arithmetic number, because the mean of its divisors is an integer number (958272).

Almost surely, 2^21043780 is an apocalyptic number.

21043780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21043780 is an abundant number, since it is smaller than the sum of its proper divisors (24953276).

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

21043780 is a wasteful number, since it uses less digits than its factorization.

21043780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 484 (or 482 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21043780 is about 4587.3499975476. The cubic root of 21043780 is about 276.0840078937.

Adding to 21043780 its reverse (8734012), we get a palindrome (29777792).

The spelling of 21043780 in words is "twenty-one million, forty-three thousand, seven hundred eighty".