21034820 has 24 divisors (see below), whose sum is σ = 44583000. Its totient is φ = 8335872.

The previous prime is 21034807. The next prime is 21034823. The reversal of 21034820 is 2843012.

It can be written as a sum of positive squares in 4 ways, for example, as 802816 + 20232004 = 896^2 + 4498^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21034792 and 21034801.

It is not an unprimeable number, because it can be changed into a prime (21034823) 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 7 ways as a sum of consecutive naturals, for example, 2645 + ... + 7004.

It is an arithmetic number, because the mean of its divisors is an integer number (1857625).

Almost surely, 2^21034820 is an apocalyptic number.

21034820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21034820 is an abundant number, since it is smaller than the sum of its proper divisors (23548180).

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

21034820 is a wasteful number, since it uses less digits than its factorization.

21034820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9767 (or 9765 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21034820 is about 4586.3732948813. The cubic root of 21034820 is about 276.0448187386.

Adding to 21034820 its reverse (2843012), we get a palindrome (23877832).

The spelling of 21034820 in words is "twenty-one million, thirty-four thousand, eight hundred twenty".