20561797 has 2 divisors, whose sum is σ = 20561798. Its totient is φ = 20561796.

The previous prime is 20561777. The next prime is 20561809. The reversal of 20561797 is 79716502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19236996 + 1324801 = 4386^2 + 1151^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20561797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20561707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10280898 + 10280899.

It is an arithmetic number, because the mean of its divisors is an integer number (10280899).

Almost surely, 2^20561797 is an apocalyptic number.

It is an amenable number.

20561797 is a deficient number, since it is larger than the sum of its proper divisors (1).

20561797 is an equidigital number, since it uses as much as digits as its factorization.

20561797 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 26460, while the sum is 37.

The square root of 20561797 is about 4534.5117708525. The cubic root of 20561797 is about 273.9599147497.

The spelling of 20561797 in words is "twenty million, five hundred sixty-one thousand, seven hundred ninety-seven".