21020777 has 2 divisors, whose sum is σ = 21020778. Its totient is φ = 21020776.

The previous prime is 21020761. The next prime is 21020803. The reversal of 21020777 is 77702012.

It is an a-pointer prime, because the next prime (21020803) can be obtained adding 21020777 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20894041 + 126736 = 4571^2 + 356^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020777 - 2⁴ = 21020761 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21023777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510388 + 10510389.

It is an arithmetic number, because the mean of its divisors is an integer number (10510389).

Almost surely, 2^21020777 is an apocalyptic number.

It is an amenable number.

21020777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020777 is an equidigital number, since it uses as much as digits as its factorization.

21020777 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1372, while the sum is 26.

The square root of 21020777 is about 4584.8420910649. The cubic root of 21020777 is about 275.9833752151.

Adding to 21020777 its reverse (77702012), we get a palindrome (98722789).

The spelling of 21020777 in words is "twenty-one million, twenty thousand, seven hundred seventy-seven".