2778356821 has 2 divisors, whose sum is σ = 2778356822. Its totient is φ = 2778356820.

The previous prime is 2778356761. The next prime is 2778356827. The reversal of 2778356821 is 1286538772.

2778356821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2329510225 + 448846596 = 48265^2 + 21186^2 .

It is a cyclic number.

It is not a de Polignac number, because 2778356821 - 2¹⁵ = 2778324053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2778356827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1389178410 + 1389178411.

It is an arithmetic number, because the mean of its divisors is an integer number (1389178411).

Almost surely, 2^2778356821 is an apocalyptic number.

It is an amenable number.

2778356821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2778356821 is an equidigital number, since it uses as much as digits as its factorization.

2778356821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1128960, while the sum is 49.

The square root of 2778356821 is about 52710.1206695640. The cubic root of 2778356821 is about 1405.8187788436.

The spelling of 2778356821 in words is "two billion, seven hundred seventy-eight million, three hundred fifty-six thousand, eight hundred twenty-one".