21242569 has 2 divisors, whose sum is σ = 21242570. Its totient is φ = 21242568.

The previous prime is 21242563. The next prime is 21242591. The reversal of 21242569 is 96524212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19316025 + 1926544 = 4395^2 + 1388^2 .

It is a cyclic number.

It is not a de Polignac number, because 21242569 - 2¹⁵ = 21209801 is a prime.

It is a super-2 number, since 2×21242569² = 902493475439522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21242569.

It is not a weakly prime, because it can be changed into another prime (21242563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621284 + 10621285.

It is an arithmetic number, because the mean of its divisors is an integer number (10621285).

Almost surely, 2^21242569 is an apocalyptic number.

It is an amenable number.

21242569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242569 is an equidigital number, since it uses as much as digits as its factorization.

21242569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 31.

The square root of 21242569 is about 4608.9661530543. The cubic root of 21242569 is about 276.9506226418.

It can be divided in two parts, 2124 and 2569, that multiplied together give a triangular number (5456556 = T₃₃₀₃).

The spelling of 21242569 in words is "twenty-one million, two hundred forty-two thousand, five hundred sixty-nine".