20689657 has 2 divisors, whose sum is σ = 20689658. Its totient is φ = 20689656.

The previous prime is 20689649. The next prime is 20689661. The reversal of 20689657 is 75698602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17464041 + 3225616 = 4179^2 + 1796^2 .

It is a cyclic number.

It is not a de Polignac number, because 20689657 - 2³ = 20689649 is a prime.

It is not a weakly prime, because it can be changed into another prime (20689457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10344828 + 10344829.

It is an arithmetic number, because the mean of its divisors is an integer number (10344829).

Almost surely, 2^20689657 is an apocalyptic number.

It is an amenable number.

20689657 is a deficient number, since it is larger than the sum of its proper divisors (1).

20689657 is an equidigital number, since it uses as much as digits as its factorization.

20689657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 181440, while the sum is 43.

The square root of 20689657 is about 4548.5884623694. The cubic root of 20689657 is about 274.5265993027.

The spelling of 20689657 in words is "twenty million, six hundred eighty-nine thousand, six hundred fifty-seven".