20640647 has 2 divisors, whose sum is σ = 20640648. Its totient is φ = 20640646.

The previous prime is 20640617. The next prime is 20640667. The reversal of 20640647 is 74604602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20640647 - 2⁶ = 20640583 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20640617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10320323 + 10320324.

It is an arithmetic number, because the mean of its divisors is an integer number (10320324).

Almost surely, 2^20640647 is an apocalyptic number.

20640647 is a deficient number, since it is larger than the sum of its proper divisors (1).

20640647 is an equidigital number, since it uses as much as digits as its factorization.

20640647 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 29.

The square root of 20640647 is about 4543.1978825493. The cubic root of 20640647 is about 274.3096602074.

The spelling of 20640647 in words is "twenty million, six hundred forty thousand, six hundred forty-seven".