20558861 has 2 divisors, whose sum is σ = 20558862. Its totient is φ = 20558860.

The previous prime is 20558843. The next prime is 20558897. The reversal of 20558861 is 16885502.

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., 20529961 + 28900 = 4531^2 + 170^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20558861 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20558821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10279430 + 10279431.

It is an arithmetic number, because the mean of its divisors is an integer number (10279431).

Almost surely, 2^20558861 is an apocalyptic number.

It is an amenable number.

20558861 is a deficient number, since it is larger than the sum of its proper divisors (1).

20558861 is an equidigital number, since it uses as much as digits as its factorization.

20558861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19200, while the sum is 35.

The square root of 20558861 is about 4534.1880199215. The cubic root of 20558861 is about 273.9468746347.

The spelling of 20558861 in words is "twenty million, five hundred fifty-eight thousand, eight hundred sixty-one".