21243769 has 2 divisors, whose sum is σ = 21243770. Its totient is φ = 21243768.

The previous prime is 21243731. The next prime is 21243779. The reversal of 21243769 is 96734212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19713600 + 1530169 = 4440^2 + 1237^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243769 is a prime.

It is a super-2 number, since 2×21243769² = 902595442650722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21243709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621884 + 10621885.

It is an arithmetic number, because the mean of its divisors is an integer number (10621885).

Almost surely, 2^21243769 is an apocalyptic number.

It is an amenable number.

21243769 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243769 is an equidigital number, since it uses as much as digits as its factorization.

21243769 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 34.

The square root of 21243769 is about 4609.0963322543. The cubic root of 21243769 is about 276.9558375554.

The spelling of 21243769 in words is "twenty-one million, two hundred forty-three thousand, seven hundred sixty-nine".