20921707 has 2 divisors, whose sum is σ = 20921708. Its totient is φ = 20921706.

The previous prime is 20921701. The next prime is 20921711. The reversal of 20921707 is 70712902.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20921707 - 2²³ = 12533099 is a prime.

It is not a weakly prime, because it can be changed into another prime (20921701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460853 + 10460854.

It is an arithmetic number, because the mean of its divisors is an integer number (10460854).

Almost surely, 2^20921707 is an apocalyptic number.

20921707 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921707 is an equidigital number, since it uses as much as digits as its factorization.

20921707 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1764, while the sum is 28.

The square root of 20921707 is about 4574.0252513514. The cubic root of 20921707 is about 275.5491264530.

The spelling of 20921707 in words is "twenty million, nine hundred twenty-one thousand, seven hundred seven".