21210769 has 2 divisors, whose sum is σ = 21210770. Its totient is φ = 21210768.

The previous prime is 21210767. The next prime is 21210773. The reversal of 21210769 is 96701212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16851025 + 4359744 = 4105^2 + 2088^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210769 - 2¹ = 21210767 is a prime.

It is a super-2 number, since 2×21210769² = 899793443142722, which contains 22 as substring.

Together with 21210767, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21210767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605384 + 10605385.

It is an arithmetic number, because the mean of its divisors is an integer number (10605385).

Almost surely, 2^21210769 is an apocalyptic number.

It is an amenable number.

21210769 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210769 is an equidigital number, since it uses as much as digits as its factorization.

21210769 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21210769 is about 4605.5150634864. The cubic root of 21210769 is about 276.8123558099.

The spelling of 21210769 in words is "twenty-one million, two hundred ten thousand, seven hundred sixty-nine".