20155020661 has 2 divisors, whose sum is σ = 20155020662. Its totient is φ = 20155020660.

The previous prime is 20155020649. The next prime is 20155020707. The reversal of 20155020661 is 16602055102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13617489636 + 6537531025 = 116694^2 + 80855^2 .

It is a cyclic number.

It is not a de Polignac number, because 20155020661 - 2²⁷ = 20020802933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20155020961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10077510330 + 10077510331.

It is an arithmetic number, because the mean of its divisors is an integer number (10077510331).

Almost surely, 2^20155020661 is an apocalyptic number.

It is an amenable number.

20155020661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20155020661 is an equidigital number, since it uses as much as digits as its factorization.

20155020661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3600, while the sum is 28.

Adding to 20155020661 its reverse (16602055102), we get a palindrome (36757075763).

The spelling of 20155020661 in words is "twenty billion, one hundred fifty-five million, twenty thousand, six hundred sixty-one".