20136521861 has 2 divisors, whose sum is σ = 20136521862. Its totient is φ = 20136521860.

The previous prime is 20136521843. The next prime is 20136521887. The reversal of 20136521861 is 16812563102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10472452225 + 9664069636 = 102335^2 + 98306^2 .

It is a cyclic number.

It is not a de Polignac number, because 20136521861 - 2¹⁰ = 20136520837 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20136521891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10068260930 + 10068260931.

It is an arithmetic number, because the mean of its divisors is an integer number (10068260931).

Almost surely, 2^20136521861 is an apocalyptic number.

It is an amenable number.

20136521861 is a deficient number, since it is larger than the sum of its proper divisors (1).

20136521861 is an equidigital number, since it uses as much as digits as its factorization.

20136521861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 35.

The spelling of 20136521861 in words is "twenty billion, one hundred thirty-six million, five hundred twenty-one thousand, eight hundred sixty-one".