20645917 has 2 divisors, whose sum is σ = 20645918. Its totient is φ = 20645916.

The previous prime is 20645903. The next prime is 20645921. The reversal of 20645917 is 71954602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13388281 + 7257636 = 3659^2 + 2694^2 .

It is a cyclic number.

It is not a de Polignac number, because 20645917 - 2¹⁵ = 20613149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20645957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10322958 + 10322959.

It is an arithmetic number, because the mean of its divisors is an integer number (10322959).

Almost surely, 2^20645917 is an apocalyptic number.

It is an amenable number.

20645917 is a deficient number, since it is larger than the sum of its proper divisors (1).

20645917 is an equidigital number, since it uses as much as digits as its factorization.

20645917 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 20645917 is about 4543.7778334773. Note that the first 3 decimals coincide. The cubic root of 20645917 is about 274.3330039345. Note that the first 3 decimals are identical.

The spelling of 20645917 in words is "twenty million, six hundred forty-five thousand, nine hundred seventeen".