20972209 has 4 divisors (see below), whose sum is σ = 21237760. Its totient is φ = 20706660.

The previous prime is 20972179. The next prime is 20972221. The reversal of 20972209 is 90227902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20972209 - 2⁹ = 20971697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20972269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132657 + ... + 132814.

It is an arithmetic number, because the mean of its divisors is an integer number (5309440).

Almost surely, 2^20972209 is an apocalyptic number.

It is an amenable number.

20972209 is a deficient number, since it is larger than the sum of its proper divisors (265551).

20972209 is an equidigital number, since it uses as much as digits as its factorization.

20972209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265550.

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 20972209 is about 4579.5424443933. The cubic root of 20972209 is about 275.7706603217.

The spelling of 20972209 in words is "twenty million, nine hundred seventy-two thousand, two hundred nine".