21020021177 has 2 divisors, whose sum is σ = 21020021178. Its totient is φ = 21020021176.

The previous prime is 21020021147. The next prime is 21020021203. The reversal of 21020021177 is 77112002012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14865461776 + 6154559401 = 121924^2 + 78451^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020021177 - 2¹⁶ = 21019955641 is a prime.

It is not a weakly prime, because it can be changed into another prime (21020021137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510010588 + 10510010589.

It is an arithmetic number, because the mean of its divisors is an integer number (10510010589).

Almost surely, 2^21020021177 is an apocalyptic number.

It is an amenable number.

21020021177 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020021177 is an equidigital number, since it uses as much as digits as its factorization.

21020021177 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 392, while the sum is 23.

Adding to 21020021177 its reverse (77112002012), we get a palindrome (98132023189).

The spelling of 21020021177 in words is "twenty-one billion, twenty million, twenty-one thousand, one hundred seventy-seven".