21084780 has 24 divisors (see below), whose sum is σ = 59037552. Its totient is φ = 5622592.

The previous prime is 21084779. The next prime is 21084787. The reversal of 21084780 is 8748012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (21084787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175647 + ... + 175766.

It is an arithmetic number, because the mean of its divisors is an integer number (2459898).

Almost surely, 2^21084780 is an apocalyptic number.

21084780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21084780 is an abundant number, since it is smaller than the sum of its proper divisors (37952772).

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

21084780 is a wasteful number, since it uses less digits than its factorization.

21084780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351425 (or 351423 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 21084780 is about 4591.8166339696. The cubic root of 21084780 is about 276.2631914969.

The spelling of 21084780 in words is "twenty-one million, eighty-four thousand, seven hundred eighty".