21220009 has 8 divisors (see below), whose sum is σ = 21674952. Its totient is φ = 20768640.

The previous prime is 21219997. The next prime is 21220019. The reversal of 21220009 is 90002212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 426409 + 20793600 = 653^2 + 4560^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21220009 - 2⁵ = 21219977 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21219974 and 21220001.

It is not an unprimeable number, because it can be changed into a prime (21220019) 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, 13467 + ... + 14959.

It is an arithmetic number, because the mean of its divisors is an integer number (2709369).

Almost surely, 2^21220009 is an apocalyptic number.

It is an amenable number.

21220009 is a deficient number, since it is larger than the sum of its proper divisors (454943).

21220009 is a wasteful number, since it uses less digits than its factorization.

21220009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1787.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21220009 is about 4606.5180993892. The cubic root of 21220009 is about 276.8525456909.

The spelling of 21220009 in words is "twenty-one million, two hundred twenty thousand, nine".