20778226661 has 2 divisors, whose sum is σ = 20778226662. Its totient is φ = 20778226660.

The previous prime is 20778226649. The next prime is 20778226681. The reversal of 20778226661 is 16662287702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13775716900 + 7002509761 = 117370^2 + 83681^2 .

It is a cyclic number.

It is not a de Polignac number, because 20778226661 - 2¹⁸ = 20777964517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20778226631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10389113330 + 10389113331.

It is an arithmetic number, because the mean of its divisors is an integer number (10389113331).

Almost surely, 2^20778226661 is an apocalyptic number.

It is an amenable number.

20778226661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20778226661 is an equidigital number, since it uses as much as digits as its factorization.

20778226661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 677376, while the sum is 47.

The spelling of 20778226661 in words is "twenty billion, seven hundred seventy-eight million, two hundred twenty-six thousand, six hundred sixty-one".