21220605 has 96 divisors (see below), whose sum is σ = 45826560. Its totient is φ = 8870400.

The previous prime is 21220601. The next prime is 21220613. The reversal of 21220605 is 50602212.

It is not a de Polignac number, because 21220605 - 2² = 21220601 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220601) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 210055 + ... + 210155.

It is an arithmetic number, because the mean of its divisors is an integer number (477360).

Almost surely, 2^21220605 is an apocalyptic number.

It is an amenable number.

21220605 is an abundant number, since it is smaller than the sum of its proper divisors (24605955).

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

21220605 is a wasteful number, since it uses less digits than its factorization.

21220605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171 (or 168 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21220605 is about 4606.5827898780. The cubic root of 21220605 is about 276.8551376247.

Adding to 21220605 its reverse (50602212), we get a palindrome (71822817).

The spelling of 21220605 in words is "twenty-one million, two hundred twenty thousand, six hundred five".