20642360561 has 2 divisors, whose sum is σ = 20642360562. Its totient is φ = 20642360560.

The previous prime is 20642360509. The next prime is 20642360591. The reversal of 20642360561 is 16506324602.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17359643536 + 3282717025 = 131756^2 + 57295^2 .

It is a cyclic number.

It is not a de Polignac number, because 20642360561 - 2²² = 20638166257 is a prime.

It is a super-2 number, since 2×20642360561² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20642360591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10321180280 + 10321180281.

It is an arithmetic number, because the mean of its divisors is an integer number (10321180281).

Almost surely, 2^20642360561 is an apocalyptic number.

It is an amenable number.

20642360561 is a deficient number, since it is larger than the sum of its proper divisors (1).

20642360561 is an equidigital number, since it uses as much as digits as its factorization.

20642360561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 35.

The spelling of 20642360561 in words is "twenty billion, six hundred forty-two million, three hundred sixty thousand, five hundred sixty-one".