20535661 has 2 divisors, whose sum is σ = 20535662. Its totient is φ = 20535660.

The previous prime is 20535659. The next prime is 20535689. The reversal of 20535661 is 16653502.

It is an a-pointer prime, because the next prime (20535689) can be obtained adding 20535661 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13213225 + 7322436 = 3635^2 + 2706^2 .

It is a cyclic number.

It is not a de Polignac number, because 20535661 - 2¹ = 20535659 is a prime.

Together with 20535659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20535601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10267830 + 10267831.

It is an arithmetic number, because the mean of its divisors is an integer number (10267831).

Almost surely, 2^20535661 is an apocalyptic number.

It is an amenable number.

20535661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20535661 is an equidigital number, since it uses as much as digits as its factorization.

20535661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 20535661 is about 4531.6289565674. The cubic root of 20535661 is about 273.8437891626.

The spelling of 20535661 in words is "twenty million, five hundred thirty-five thousand, six hundred sixty-one".