21290777 has 2 divisors, whose sum is σ = 21290778. Its totient is φ = 21290776.

The previous prime is 21290761. The next prime is 21290779. The reversal of 21290777 is 77709212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10896601 + 10394176 = 3301^2 + 3224^2 .

It is a cyclic number.

It is not a de Polignac number, because 21290777 - 2⁴ = 21290761 is a prime.

Together with 21290779, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21290779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645388 + 10645389.

It is an arithmetic number, because the mean of its divisors is an integer number (10645389).

Almost surely, 2^21290777 is an apocalyptic number.

It is an amenable number.

21290777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21290777 is an equidigital number, since it uses as much as digits as its factorization.

21290777 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12348, while the sum is 35.

The square root of 21290777 is about 4614.1929955302. The cubic root of 21290777 is about 277.1599687672.

Adding to 21290777 its reverse (77709212), we get a palindrome (98999989).

The spelling of 21290777 in words is "twenty-one million, two hundred ninety thousand, seven hundred seventy-seven".