20621209 has 12 divisors (see below), whose sum is σ = 24548304. Its totient is φ = 17262504.

The previous prime is 20621191. The next prime is 20621239. The reversal of 20621209 is 90212602.

It is a happy number.

It is not a de Polignac number, because 20621209 - 2⁵ = 20621177 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20621209.

It is not an unprimeable number, because it can be changed into a prime (20621239) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2787 + ... + 7000.

It is an arithmetic number, because the mean of its divisors is an integer number (2045692).

Almost surely, 2^20621209 is an apocalyptic number.

It is an amenable number.

20621209 is a deficient number, since it is larger than the sum of its proper divisors (3927095).

20621209 is an equidigital number, since it uses as much as digits as its factorization.

20621209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9844 (or 9837 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 20621209 is about 4541.0581366021. The cubic root of 20621209 is about 274.2235242473.

The spelling of 20621209 in words is "twenty million, six hundred twenty-one thousand, two hundred nine".