21245620 has 48 divisors (see below), whose sum is σ = 48988800. Its totient is φ = 7675520.

The previous prime is 21245617. The next prime is 21245669. The reversal of 21245620 is 2654212.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a junction number, because it is equal to n+sod(n) for n = 21245591 and 21245600.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 59001 + ... + 59359.

It is an arithmetic number, because the mean of its divisors is an integer number (1020600).

Almost surely, 2^21245620 is an apocalyptic number.

21245620 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 21245620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24494400).

21245620 is an abundant number, since it is smaller than the sum of its proper divisors (27743180).

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

21245620 is a wasteful number, since it uses less digits than its factorization.

21245620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 648 (or 646 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 22.

The square root of 21245620 is about 4609.2971264608. The cubic root of 21245620 is about 276.9638811747.

Adding to 21245620 its reverse (2654212), we get a palindrome (23899832).

It can be divided in two parts, 2124 and 5620, that added together give a square (7744 = 88²).

The spelling of 21245620 in words is "twenty-one million, two hundred forty-five thousand, six hundred twenty".