20669921 has 2 divisors, whose sum is σ = 20669922. Its totient is φ = 20669920.

The previous prime is 20669917. The next prime is 20669933. The reversal of 20669921 is 12996602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16000000 + 4669921 = 4000^2 + 2161^2 .

It is a cyclic number.

It is not a de Polignac number, because 20669921 - 2² = 20669917 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20669941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10334960 + 10334961.

It is an arithmetic number, because the mean of its divisors is an integer number (10334961).

Almost surely, 2^20669921 is an apocalyptic number.

It is an amenable number.

20669921 is a deficient number, since it is larger than the sum of its proper divisors (1).

20669921 is an equidigital number, since it uses as much as digits as its factorization.

20669921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 20669921 is about 4546.4184805185. The cubic root of 20669921 is about 274.4392806222.

The spelling of 20669921 in words is "twenty million, six hundred sixty-nine thousand, nine hundred twenty-one".