20664257 has 2 divisors, whose sum is σ = 20664258. Its totient is φ = 20664256.

The previous prime is 20664239. The next prime is 20664289. The reversal of 20664257 is 75246602.

It is an a-pointer prime, because the next prime (20664289) can be obtained adding 20664257 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20214016 + 450241 = 4496^2 + 671^2 .

It is a cyclic number.

It is not a de Polignac number, because 20664257 - 2¹² = 20660161 is a prime.

It is not a weakly prime, because it can be changed into another prime (20661257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10332128 + 10332129.

It is an arithmetic number, because the mean of its divisors is an integer number (10332129).

Almost surely, 2^20664257 is an apocalyptic number.

It is an amenable number.

20664257 is a deficient number, since it is larger than the sum of its proper divisors (1).

20664257 is an equidigital number, since it uses as much as digits as its factorization.

20664257 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 32.

The square root of 20664257 is about 4545.7955299375. The cubic root of 20664257 is about 274.4142109233.

The spelling of 20664257 in words is "twenty million, six hundred sixty-four thousand, two hundred fifty-seven".