21620356 has 12 divisors (see below), whose sum is σ = 38029068. Its totient is φ = 10754912.

The previous prime is 21620323. The next prime is 21620359. The reversal of 21620356 is 65302612.

It can be written as a sum of positive squares in 2 ways, for example, as 17556100 + 4064256 = 4190^2 + 2016^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21620356.

It is not an unprimeable number, because it can be changed into a prime (21620359) 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 3 ways as a sum of consecutive naturals, for example, 12931 + ... + 14506.

It is an arithmetic number, because the mean of its divisors is an integer number (3169089).

Almost surely, 2^21620356 is an apocalyptic number.

It is an amenable number.

21620356 is a deficient number, since it is larger than the sum of its proper divisors (16408712).

21620356 is a wasteful number, since it uses less digits than its factorization.

21620356 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27638 (or 27636 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 21620356 is about 4649.7694566505. The cubic root of 21620356 is about 278.5827879028.

Adding to 21620356 its reverse (65302612), we get a palindrome (86922968).

The spelling of 21620356 in words is "twenty-one million, six hundred twenty thousand, three hundred fifty-six".