20688121 has 2 divisors, whose sum is σ = 20688122. Its totient is φ = 20688120.

The previous prime is 20688113. The next prime is 20688197. The reversal of 20688121 is 12188602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19678096 + 1010025 = 4436^2 + 1005^2 .

It is a cyclic number.

It is not a de Polignac number, because 20688121 - 2³ = 20688113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20688121.

It is not a weakly prime, because it can be changed into another prime (20688721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10344060 + 10344061.

It is an arithmetic number, because the mean of its divisors is an integer number (10344061).

Almost surely, 2^20688121 is an apocalyptic number.

It is an amenable number.

20688121 is a deficient number, since it is larger than the sum of its proper divisors (1).

20688121 is an equidigital number, since it uses as much as digits as its factorization.

20688121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1536, while the sum is 28.

The square root of 20688121 is about 4548.4196156467. The cubic root of 20688121 is about 274.5198055170.

The spelling of 20688121 in words is "twenty million, six hundred eighty-eight thousand, one hundred twenty-one".