20408561 has 2 divisors, whose sum is σ = 20408562. Its totient is φ = 20408560.

The previous prime is 20408543. The next prime is 20408573. The reversal of 20408561 is 16580402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19891600 + 516961 = 4460^2 + 719^2 .

It is a cyclic number.

It is not a de Polignac number, because 20408561 - 2¹⁰ = 20407537 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20408561.

It is not a weakly prime, because it can be changed into another prime (20408581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10204280 + 10204281.

It is an arithmetic number, because the mean of its divisors is an integer number (10204281).

Almost surely, 2^20408561 is an apocalyptic number.

It is an amenable number.

20408561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20408561 is an equidigital number, since it uses as much as digits as its factorization.

20408561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 20408561 is about 4517.5835354756. The cubic root of 20408561 is about 273.2776585329.

Adding to 20408561 its reverse (16580402), we get a palindrome (36988963).

It can be divided in two parts, 2040 and 8561, that added together give a palindrome (10601).

The spelling of 20408561 in words is "twenty million, four hundred eight thousand, five hundred sixty-one".