20663509 has 2 divisors, whose sum is σ = 20663510. Its totient is φ = 20663508.

The previous prime is 20663497. The next prime is 20663543. The reversal of 20663509 is 90536602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16240900 + 4422609 = 4030^2 + 2103^2 .

It is a cyclic number.

It is not a de Polignac number, because 20663509 - 2¹⁷ = 20532437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20663569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10331754 + 10331755.

It is an arithmetic number, because the mean of its divisors is an integer number (10331755).

Almost surely, 2^20663509 is an apocalyptic number.

It is an amenable number.

20663509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20663509 is an equidigital number, since it uses as much as digits as its factorization.

20663509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9720, while the sum is 31.

The square root of 20663509 is about 4545.7132553649. The cubic root of 20663509 is about 274.4108998226.

The spelling of 20663509 in words is "twenty million, six hundred sixty-three thousand, five hundred nine".