20516861 has 2 divisors, whose sum is σ = 20516862. Its totient is φ = 20516860.

The previous prime is 20516849. The next prime is 20516887. The reversal of 20516861 is 16861502.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16556761 + 3960100 = 4069^2 + 1990^2 .

It is a cyclic number.

It is not a de Polignac number, because 20516861 - 2¹⁰ = 20515837 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20516831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10258430 + 10258431.

It is an arithmetic number, because the mean of its divisors is an integer number (10258431).

Almost surely, 2^20516861 is an apocalyptic number.

It is an amenable number.

20516861 is a deficient number, since it is larger than the sum of its proper divisors (1).

20516861 is an equidigital number, since it uses as much as digits as its factorization.

20516861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 29.

The square root of 20516861 is about 4529.5541723220. The cubic root of 20516861 is about 273.7601974197.

The spelling of 20516861 in words is "twenty million, five hundred sixteen thousand, eight hundred sixty-one".