20426561 has 2 divisors, whose sum is σ = 20426562. Its totient is φ = 20426560.

The previous prime is 20426557. The next prime is 20426573. The reversal of 20426561 is 16562402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18879025 + 1547536 = 4345^2 + 1244^2 .

It is a cyclic number.

It is not a de Polignac number, because 20426561 - 2² = 20426557 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 20426561.

It is not a weakly prime, because it can be changed into another prime (20426761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10213280 + 10213281.

It is an arithmetic number, because the mean of its divisors is an integer number (10213281).

Almost surely, 2^20426561 is an apocalyptic number.

It is an amenable number.

20426561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20426561 is an equidigital number, since it uses as much as digits as its factorization.

20426561 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 26.

The square root of 20426561 is about 4519.5753119071. The cubic root of 20426561 is about 273.3579769902.

Adding to 20426561 its reverse (16562402), we get a palindrome (36988963).

The spelling of 20426561 in words is "twenty million, four hundred twenty-six thousand, five hundred sixty-one".